Your problem sounds like a typical case of engine knock. If you dont have an SVT try using premium gas on your next fill up, I bet that will cure it. If you do have an svt, and you have that problem then you must have a bad knock sensor.
Shawn Mims
98 Silver SVT
180k miles
#1859
15% tint(rear 3) 35%(side 2)
Sony cd-rw/mp3 player