[Fire TV General] Skel40:
Before I start this tweaking guide for the Fire TV Stick 4K/Lite/3rd Gen, I'm not responsible for what you do to your device. Please follow this guide carefully to prevent confusion. First of all, you need to be rooted and unlocked to add these tweaks to your Fire TV Stick 4K. You also need a USB keyboard or a Bluetooth keyboard to successfully type in these tweaks yourself in the file, build.prop. Due to Amazon's operating system, typing these tweaks in will redirect you to the top page in which prevents being able to scroll down to an empty line if you do end up using the Amazon Fire TV remote/controller. It's important to not accidently make the Amazon Keyboard pop up. A sidenote too, using the Fire TV remote app while copying and pasting will not work therefore will lead to the code you pasted to show up as /. Go to the Amazon Appstore and install Total Commander, you need to hover over to file system root, Grant su permissions, go to system, then long press the build.prop file and press edit file, (use Total Commander's editor). Reboot after applying these tweaks!!! With your keyboard press and hold the arrow down to scroll to the last line and hit enter, then add the build.prop tweaks listed below:

Build.prop Tweaks:

Better Scrolling

windowsmgr.max_events_per_sec=150

ro.min_pointer_dur=8

ro.max.fling_velocity=12000

ro.min.fling_velocity=8000

persist.sys.scrollingcache=3

debug.sf.hw=1

Modify Logcat:

logcat.live=disable

Quicker Boot Up:

ro.config.hw_quickpoweron=true

Disable Boot Animation (Optional)

debug.sf.nobootanimation=1

Modify Error Profiler:

profiler.force_disable_err_rpt=1

profiler.force_disable_ulog=1

ro.kernel.checkjni=0

ro.kernel.android.checkjni=0

Disable Strict Mode Checking:

persist.android.strictmode=0

Improve Touch Responsiveness and Hardware Rendering:

persist.sys.ui.hw=1

debug.performance.tuning=1

video.accelerate.hw=1

debug.egl.profiler=1

debug.egl.hw=1

debug.composition.type=gpu

Stream Faster:

media.stagefright.enable-player=true

media.stagefright.enable-meta=true

media.stagefright.enable-scan=true

media.stagefright.enable-http=true

media.stagefright.enable-rtsp=true

media.stagefright.enable-record=true

media.stagefright.enable-aac=true

media.stagefright.enable-qcp=true

Better Signal Strength (Helps when internet has poor latency):

persist.cust.tel.eons=1

ro.config.hw_fast_dormancy=1

Disable Sending Usage of Data:

ro.config.nocheckin=1

Improved Net Buffersize:

net.tcp.buffersize.default=4096,87380,256960, 16384,256960

net.tcp.buffersize.wifi=4096,87380,256960,40984,256960

net.tcp.buffersize.hsdpa=6144,87380,1048576, 7380,1048576

net.tcp.buffersize.hspa=6144,87380,524288,6184,262144

net.tcp.buffersize.umts=4096,87380,256960,4084,256960

net.tcp.buffersize.edge=4096,87380,256960,4084,256960

net.tcp.buffersize.gprs=4096,87380,256960,4084,256960

net.tcp.buffersize.evdo_b=6144,87380,104857,87880,1048576

IPv6 and IPv4 Tweaks (You can disable IPv6 if optional)

IPv4

net.ipv4.tcp_ecn=0

net.ipv4.route.flush=1

net.ipv4.tcp_rfc1337=1

net.ipv4.ip_no_pmtu_disc=0

net.ipv4.tcp_sack=1

net.ipv4.tcp_fack=1

net.ipv4.tcp_window_scaling=1

net.ipv4.tcp_timestamps=0

net.ipv4.tcp_rmem='6144 87380 1048576'

net.ipv4.tcp_wmem='6144 87380 1048576'

net.ipv4.tcp_mem='187000 187000 187000'

net.ipv4.tcp_no_metrics_save=1

net.ipv4.icmp_echo_ignore_all=1

net.ipv4.tcp_moderate_rcvbuf=1

net.ipv4.conf.all.accept_redirects=0

net.ipv4.conf.default.accept_redirects=0

net.ipv4.conf.all.rp_filter=1

#net.ipv4.conf.<device>.rp_filter=1

net.ipv4.conf.default.rp_filter=1

net.ipv4.conf.all.send_redirects=0

net.ipv4.conf.default.send_redirects=0

net.ipv4.conf.all.secure_redirects=0

net.ipv4.conf.default.secure_redirects=0

net.ipv4.conf.all.accept_source_route=0

net.ipv4.conf.default.accept_source_route=0

net.ipv4.udp_rmem_min=6144

net.ipv4.udp_wmem_min=6144

net.ipv4.tcp_tw_recycle=1

net.ipv4.tcp_tw_reuse=1

net.ipv4.tcp_syncookies=1

net.ipv4.tcp_synack_retries=2

net.ipv4.tcp_syn_retries=2

net.ipv4.tcp_max_syn_backlog=1024

net.ipv4.tcp_max_tw_buckets=16384

net.ipv4.icmp_echo_ignore_broadcasts=1

net.ipv4.icmp_ignore_bogus_error_responses=1

net.ipv4.tcp_fin_timeout=15

net.ipv4.tcp_keepalive_intvl=30

net.ipv4.tcp_keepalive_probes=5

net.ipv4.tcp_keepalive_time=1800

net.ipv4.ip_forward=0

#

#net.tcp.default_init_rwnd=60

#

# IPv6

#net.ipv6.conf.all.accept_redirects=0

#net.ipv6.conf.default.accept_redirects=0

#net.ipv6.conf.all.use_tempaddr=2

#net.ipv6.conf.default.use_tempaddr=2

# Disable IPv6

net.ipv6.conf.all.disable_ipv6=1 #echo "0" > /proc/sys/net/ipv6/conf/wlan0/disable_ipv6

net.ipv6.conf.default.disable_ipv6=1

#net.ipv6.conf.$WIFI.disable_ipv6=1

Enable ADB and Disable USB Debugging Pop-up

persist.adb.notify=0

persist.service.adb.enable=1

persist.service.debuggable=1

persist.sys.usb.config=mtp,adb

More RAM

persist.sys.purgeable_assets=1

persist.service.pcsync.enable=0

persist.service.lgospd.enable=0

These are all the tweaks I have added on my Fire TV Stick 4K/Lite/3rd Gen. So far it's been successful for me with performance improvements and apps that are horrible with scrolling. Let me know what you guys think! If you want even more performance out of your device on top of these tweaks to add in the build.prop, download and install Kernel Adiutor and set the CPU Governor to Performance. You'll now see it say 1690! Apply on Boot! Then reboot!

Surprisingly enough the Fire TV Stick Lite/3rd Generation Sticks have the same cpu frequencies as the Fire TV Stick 4K with .5 less of ram. You'll notice how fast your device gets with these tweaks enabled.