i have a 90 rolla and it has black smoke and it takes alot of gas. i took it to a mechanic he told me that everything look good. he did all diognostics and everything looked clean. my uncle and i checked everything out and still could not figure it out. i used 2 cans of intake cleaner through the intake valves. still smokes the spark plugs i changed and they are already black the 3rd week they been there. i put a hell alot of STP fuel injection cleaners like 2 things per fillup at the gas station, then i added 1 more when my tank was half way. i was wondering if anyone had any advice or had this similiar problem. i been pulling hair out of my head to figure this one out. please help any advice is well apprieciatted.