Ok i have EG6 with a 95 C1 swap i bought the car already swapped .
when you get into it around 6k the car starts to backfire its *** off and it sound like its comen from the the mani .i took look at it and someone took the dual flanges out and the timing is off 4 degress would this cause it ?
brand new plugs ,brand new dizzy p28 ecu also i found out after i bought it the car was boosted at one point compression is 200 across all 4 cylinders

 

also car runs fine up untill 6k

 

any ideas ?