OK, two minor problems left to go. 1)At cold start-up, still running really rich, no popping in the pipes anymore, but lite black smoke until O2 sensor warms up a bit. 2) Still have that d@mned hesitation when the throttle is opened quickly even after advancing the timing to 1 degree BTDC (which is as far as I can go with no pinging). Holley tech guys swear it's to much fuel pressure (still have stock fuel pump) but that (to me) doesn't explain the to rich cold start circuit. Before I go thru the time and expense of putting a regulator and fitting for a gage on, does anybody have anymore ideas? BTW, I have a LOT more power now and the highway cruse requires much less throttle that with the old TBI and it no longer runs out of oomph at around 3800rpm It now pulls strong (given the 33's & 3.43's) all the way to the shift points (4200rpm); /forums/images/graemlins/laugh.gif Given the mileage on the engine, I really don't want to wind it up to 5000.