Engine Cutting Out! What to check?

416 motor, W2 heads, Holley HP950, 15.1 compression, running Sunoco 112. Was having some high rpm cut out issues last week and found that it was a spark plug glazing issue. I changed out the plugs and it ran like mad. BUT, when I checked the plugs after that run, the plugs showed that it was running lean which would explain why my plugs glazed before due to too much heat in the cylinders. The other thing I noticed was that I was getting some black "peppering" on the insulator, which from what I read is the result of detonation. My speculation is that since the car was running lean, cylinder temps were getting hot. Plus with the high compression, I think the fuel was detonating. Or so that's how I am assuming what happened. I'm sure I'll hear your thoughts on that. So right now I'm just running primaries until I get it tuned right. Was running 80's on the front jets and changed to 86's. Changed my spark plug gap to .035 from .038. Checked timing and have it set to 34 total. It may have been 35-36 degrees before. Now it starts, runs, and idles fine just like before. But when I go to drive it, it will cut out beyond 2500 rpm. It just runs like crap. I can't imagine that the 86 jets would make it run like that. The spark plugs are dry with a dark tan color to them. Not wet at all so I don't think I'm flooding it. I am up in arms right now. Any ideas?