No. R-1234yf is a mildly flammable, A2L refrigerant, and has system components designed to enhance safety given that difference. R-1234yf offers emission credits toward light-duty GHG compliance goals; replacing YF with a higher GWP refrigerant like HFC-134a is considered tampering with an emissions-related component under the Clean Air Act. While the performance is similar, it is illegal to use 134a in R-1234yf systems.