Lazy Throttle

[427yenko]

Not sure if this is the right place for this but I could not find a more suitable location, so here goes.
My bone stock '69 302 has been giving me fits on throttle response changes and I thought I would pose it to the crowd to see if I might find another avenue to search down.
I have played and played with squirters and cams and I have it pretty close now but still not as good as I feel it could be.
My problem is that when I start the car cold, I have the most wicked throttle response you could imagine. I have chambered exhaust and in neutral when I snap the throttle it reacts so quickly that it literally sounds like an explosion out of the tailpipes. The issue arises after the engine gets to full operating temp. As it gradually warms up the response gets lazier until at full temp it has lost its snap. Still good clean response but so different than when it is cold.
I am running full time vacuum at idle to the distributor. All in at about 6 inches. The can adds about 16 degrees. About 16 degrees of advance at the crank and about 23 degrees mechanical. The car runs great, but that cold engine response just has me wanting more at operating temps. Cooler weather helps as in the late fall it hangs on a little longer, but summer driving causes it to dissipate quickly.
My thinking is that the warmer air and engine is causing the mixture to get richer. I have tried to take out some pump shot by adjusting the spring on the pump lever and that has helped, but I feel it still could be better. Any thoughts and is anyone else experiencing this or is this just the way it goes?
Thanks for any ideas!
Bob