Couple Problems..... Soft Code???

[Unit 5302]

The two problems may be unrelated. I would tend to agree with the comments about the engine being lean as a likely source for your top end backfiring. With the kind of horsepower I'd expect that combination to be capable of achieving with a decent tune, you'd need about 60psi on the stock injectors to simulate the stock injection cycle. You're running 39, which would be spot on for 24lb/hr units.

As Jeff stated, getting it to a dyno might not be a bad idea, considering you could easily blow the engine if you're as lean as we suspect you may be.