[JAM1775]

If you drop one jet size front & rear that should put you in the 12's on AF and net you another 10-15rwhp. In our area we have seen 2 MSD 6AL boxes with exactly the same problem you have. The MSD 6AL with their matching Master Blaster coil is an excellent system. BUT there are 6AL boxes out there that cannot rev with a rev limiter chip installed. They break up bad somewhere in the 5's. Change the chip and same result. Take out the chip and the motor pulls straight to the top. Now is the time to contact MSD and send the box to them for repair or replacement. When they bench test it they may just swap it out for you as they must know of this problem. Local race shops can becnh test it but you already know the problem is in the box.