Snowman, it's not sarcasm. Thats is why I keep suggesting supporting items to do so.
My Syclone runs 14.7 PSI stock, w/cast pistons. I made the intercooler more efficient, added methanol injection, a J&S safegaurd & added more timing, did I mention I run 24 PSI of boost now? This is on a completely 100% stock longblock engine.
How many 15 PSI blasts did you do?
Also, you are not understanding how or what an intercooler & methanol injection does for an engine. I would suggest reading up on the two.
Yes, the higher the number, the leaner the A/F ratio.
12ish is not that rich on a boosted engine, I think you are reading up on naturally aspirated engine that 12.5 is about perfect A/F ratio @ W.O.T., not so for a boosted engine.
Do some more reading on A/F ratios on turbo engines.
Snowman, Boucher just did tuning on his Holley 2BBL carb, I would suggest asking him, how he did jeting changes & mods to his carb, he did it most recently.