98 cobra with an exhaust leak that keeps coming back..HELP

[98yellsvtcobra]

Had the car for a couple of months, stock except for flowmasters and the mac h-pipe I added. I thought I would do the right thing this time- spend the extra dough and keep the exhaust legal and never have to deal with annual exhaust swaps, but God hates me apparently. When I got the new mac pipe installed initially the exhuast shop that did the labor stripped the header bolt. I took the problem to a reputable exhaust shop down the street got them to weld in a new header bolt and I thought I had my problem solved. Within a week I detected the most annoying sound ever...a slight exhaust leak. Sure enough a week later it was very noticeable. I had my friend take it back to the muffler shop that put the new bolt in and they "checked and fixed any exhuast leaks". I got my car back in the same condition basically, maybe they tightened it slightly, but a leak was still very audible. The only incident that may have initially contributed to this problem was a pretty bad bottom out on a driveway that may have mangled the exhaust a little. Another exhaust shop said that if a problem like this keeps occuring the only solution is usually to cut one end of the h pipe to adjust it so it fits flat on the collector of the header- then a leak will not spring up a week or two later. The theory makes sense, but I really don't want to mess up a $400 pipe that I just bought. Is it possible for one of the two cats to have a leak? Like I said the driveway incident was pretty rough...almost brought tears to my eyes. Is it maybe possible that the exhaust shop that installed the new header bolt could have messed the alignment up or something? If that scenario is even possible it could maybe explain why the h pipe does not want to stay sealed. The right header uses a gasket, so there is also a slim possibility that one of the exhaust shops fabricated a gasket that didn't hold up because they didn't have the right one in stock- I had a shop have to resort to that on my old saleen so I know it can happen...If anybody has a clue what I should do I am listening...I am almost about to give up, get rid of the pipe and throw on the good ole o/r h pipe and start over with a working exhaust platform. My only other question is when the exhaust bottomed out is it possible, and if so, what happens if the h pipe is pushed up against the headers harshly? Are there any other engine problems that I may have created with this scenario?