Anyone run a Street Avenger?
I just went through some very similar issues with a 750 Demon with mechanical secondaries. My setup is a bit more removed from stock than yours is, but not too much. A 360 with magnum heads, performer air gap, .525 int and exhaust (231/237 @.050) and 3000 stall.
Could not for the life of me get to the demon to keep a tune. Finally put a fuel pressure gauge on it and figured out that my fuel pressure was not high enough. Fixed all of the fuel delivery issues (High volume mechanical pump, larger lines and heat protection (the lines run a bit close to heat sources in some points) and so far it's been freakin fantastic (Don't know that larger lines were required, but they're in there now.
Tuned it when it was warmed up, and it still had a bad attitude when cold, so I added the demon choke kit. It helped A LOT! Still not the best when cold, but world's better than it was. not sure if yours has the ability to add a choke kit or not. Mine had the choke tower but did not come with a choke. Cost me something like $40 for the choke kit, and it doesn't take much to install it. I've now got almost 1000 miles on it and am loving it!
- Don