MSD streetfire problems!

I've just had a round with a Street Fire and have concluded that there is something wrong with my box too. It ran fine on the bottom end, ran ok on the top end, but would spit, sputter and backfire at cruise. I just put the HEI back in and the problem is cured. It's very disheartening because the box cleared up all my exhaust smell, which is obviously a rich mixture issue. I'm kinda thinking that there is a problem with the Rev limiter in mine. I bought mine a year ago and can't return it now. Guess that's what I get for buying parts and putting them on the shelf. Just a comment on not getting yours to power up. If you had a ballist resistor, which I'm sure you did, just use a jumper to bypass it. The ballist drops the voltage below 12v and the boxes won't run. Good luck with yours.