Please Help!! Exhaust/Fuel/Spark

[bronzit89]

Ok so I'm driving my car and all of a sudden it starts sounding like a Subaru...Lately the throttle response has had some lag so I'm guessing the fuel pump, injectors, or maybe spark?? And I also had a magnaflow muffler put on about three weeks ago. Maybe somethings loose?? Anyhow I appreciate any comments or suggestions. Thank you!

1989 325i
straight piped
everything else stock

[walktheboard]

does it lose about half the power when it sounds like a subie? i had that problem when i first got my car, it was the injector harness was loose.