Almost sounds like you have a catilictic convertor that is clogging up .......did it have any enginr codes when dealship checked it ...the only machine they have is a tech 2 to diag problem....possible fuel pump problem ...24 years @ olds dealership and there is alot of screwy type problems sometimes
ifs its a sometime problem can be a alot to diag because you can`t fix somethin that ain`t broke at the time good luck
bg
November 2005