Well, as it turns out, the engine is fine. I replaced the stupid quick fill valve with the j-tec plug and the engine peeked the 11x6 prop @ 12,800 and I ran it at 12,000 to keep it rich.

Vertical was awesome, it idles smooth and it keeps chugging the gas at all attitudes down to the last ounce. It was a pressure problem.

Concerning the oil content, I really think the difference between 18% and 20% is negligible unless you are running the engine overly lean to begin with.