I own a 98 contour se 2.5. car has 100k miles, but recent tune up, including plugs, wires, airfilter, and "performace" Y-Pipe&Cat. Oh yeah 5-spd. My problem is that the car runs fine 60% of the time and then for no known reason will get a bog type problem under full thottle at about 3500-4000 rpm, at which time the exhast will get louder and the engine runs flat/ no pwr. And at this point it doesn't tach fast. So i'm hoping that someone has run into this type of problem and has a cheaper fix.

Thanks Jason