I recently installed my off road Mac H-pipe, and had a shop weld the middle together after I installed it. The first problem is I don't think the pipes were pushed together enough cause the driver side sometimes rubs against part of the undercarriage and is somewhat annoying. My check engine light now comes on once in awhile during acceleration. And the most annoying thing is the car still misses right after 4K when it is warmed up and your getting on it hard. I already gave the car a complete tune up in an attempt to fix this. Any suggestions to these annoyances?