Mid Range RPM miss

[bonuts]

I recently put a 9:1 sbc race engine out of my circle track race car in my S10. Just working out the bugs, get it on the road and it runs good to 3500 then starts stumbling bad. Haven't seen what it will do past that range. This engine was built by a reputable builder at Tesar Engineering and has never missed a beat in my stock car. Once I get this figured out I can get back to the C10 build.

I am running a MSD 6al ignition that is relatively new but I am thinking this issue has to be ignition. I've played with timing, tried other Rev limiter chips, checked plugs to see if its running rich/lean (they look good), even thought I may not be getting enough power from alternator, grounds, etc.

Anybody have experience with the 6al setup? Is there possibly a wiring issue to the box that is causing this? Or any other hints at what might be causing this. Pretty sure its not internal, just replaced valve springs and had it looked at as the guys who built it said it was time after a season racing with this engine.

Thanks in advance.