Should have read this first. Like I said, whole lotta if's in the OP's numbers.
Also, a converter is WAY more forgiving than a clutch is. You can be off on gear and the converter isn't as bothered by it.
Also, you most likely have better headers than the OP. There is almost no HP difference between two quality over the counter headers. But a junk set of headers is a power killer. May not be the OP's issue but those fender well headers are usually a power loser.