Im having problems with my 95 Z28 recently i just started to notice my oil pressure gauge going down as the more i drive....it starts off high than after a while it will start to go down...im not to sure whats going on im thinking its an oil pump might be going but im not to sure what is leading to this also when my car gets a really bad shake when im in 6th gear but only when im on the gas pedal what do you think this could be....does have a exhaust that leaks have anything to do with it i need some help