Tuning help needed

[christer.medin at lennoxintl.com]

Hi, just subbed to this list -- I have a friend who just got his car together again, with a 379 (de-stroked 400) SBC, TPI intake, and Haltech computer.  We finally took it for a spin yesterday, and it runs great until you push the gas a little extra; at 25%+ throttle and around 2000-2500 RPM, it stumbles _badly_.  The O2 readings are in the high 700s right before then, and vacuum is at around 24", but as soon as you step on it, the O2 reading drops to 4mv, and vacuum to 5-7".  If I were to wager a guess, I'd say it appears more related to a sudden stab at the throttle than the RPMs.  Right now timing is setup for 10 degrees initial, and 36 degrees coming in full at 3K RPM.  Since you guys live and breathe ECMs, I was hoping you'd have some input here.. thanks!

Christer