would a bad cps cause poor low end perfomance and occasional back firing through throttle body when you floor it from a stand still and one more question I read on www.lunghd.com ,great site , you can use f150 front coils to give you some lift ,but what year of f150 and does it matter if its 2 wheel or 4 wheel i have a set of 98 2 wheel drive coils will they work . thks 1988 4.0 4x4

It might, but I would think that you would get an SES light. Check your timing, sounds like its a bit retarded.