straight gas is clean and surpasses all smog laws,,australian regoe authorities have this thing about 350s not complyimng with adr for pollution so straight gas fixes that..ive got 4 cars on gas ..sinbox is straight gas and is wb with 350 but its been regoed as 350 since 89 and in nsw if it runs constant rego is no probs with engineering etc..let it run out and it needs engineer cert..