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[davearm]

I am having a lower RPM (under 4200-4500rpm)lean stumble, hesiatation and general absense of power. Once I get past 4500 rpm, the motor comes alive and pulls strong until I hit the limiter. A/F at lower rpms is way lean, but from 4500 and up is fine, both on the dyno and wideband in car. I have messed with the clockspring in the AFM a bit, just a couple of notches lean from the original setting. Going to an unmolested AFM, gets rid of the problem, but I drop 3hp and some torque.
What are my options? I sometimes find myself in a corner that drops my rpm into the troublesome range, and that kills my exit speed, but downshifting to a lower gear almost instantly has the car back up against the limiter.
Would it be best to try going to a stock AFM, and play with fuel pressure, or look for some other culpret. If it is another issue, I don't want to mask it by compensating for it by playing with the fuel pressure. Or is that bad thinking?
I should be able to get some dyno time soon, and would like to have an idea of which direction to start in.
I should mention that this is a 1.6, with a good bottom end, and a new "pro" head, but the problem exhisted before the new head was installed.

Thanks,

Dave