499 stroker with a Holley 850 carb. I read the newer 850's were really 750's with an 850 TP. I've tried 750's on my 440 and they all seemed hard to tune,to rich at idle to lean at wot. very hard to get everything right. I put a pro form 950 body on an old 850 dp that uses the 850/950 tp and my combo has never ran better and every adjustment has been easy and responsive.

It just sounds like to me your carb is to small for your combo. you need more cfm IMO.