user: Question: How many bypass boosters are there on the engine with Slit exhaust ports and SPI is Yes?
Columns: ['Engine', 'Exhaust Ports', 'Bypass Ports', 'Bypass Boosters', 'SPI', 'Tapered Grind', 'Number on cyl.']
Types: ['text', 'text', 'real', 'text', 'text', 'text', 'text']
Sample row: ['Space Bug', 'Open', 2.0, '0', 'Yes', 'Yes', 'None']
SQL:

assistant: SELECT "Bypass Boosters" FROM "Table" WHERE "SPI" = 'Yes' AND "Exhaust Ports" = 'Slit';