another header leak

Over tightening the center two bolts on the header? Well, bad news, it's close to impossible (At least IMO that is) to straighten them out with heat and a hammer.

Also, you belt sanded/ground down the header flange? Big mistake since the raised welded rae is designed to press into the gasket for a interference seal.

On the collectors, same deal if there over tightened. Though you can try double and tripling up on gaskets to seal them up.

IMO, the best thing you can do is bite the bullet and get new headers and a Jegs/Summit exhaust. The cheap headers and the inexpensive exhaust @ approx under $250 is a great combo, sounds really good, nice and muscular.

Do a search here for a few of them having been done. Vid's and pictures are around here.