I haven't done it yet myself, but from what I understand you have to remove all the modifications every two years, revert the tune to stock, get your smog done, and then reinstall everything. Theres always talk of shops that will pass a car for cash, but I think the new ~2022 smog computer checks the car's computer checksum so theres no bullshitting an odb2 vehicle. I'm not a mechanic. Maybe pre odb2 cars are a loophole. My 2007 Lotus gets checked.

There's still a chance a cop cites you for illegal mods afterwards and impounds your car; but I suppose youd have to have been driving like a pretty big asshole to get them to look under your hood.

1975 and older cars are exempt.