EJ20G sputters at WOT, runs lean

Let me start off by saying that I'm a car noob; my experience with cars is limited to oil and air filter changes. I've been trying to troubleshoot this problem for a weeks now on my own and doing lots of reading, but I'm in over my head here. Any insight provided is greatly appreciated.

Problem 1 - A month ago, the car started to sputter at WOT, not a violent jerking, but more like for a split second the car loses acceleration and won't boost past 10 psi. After doing some searching, I came to the conclusion that it could be spark plugs or coil packs. I bought plugs, but haven't had the time to change them out yet. I plan to do that this weekend.

Problem 2 - Last weekend I drove a short distance to the store and noticed that it was idling rough and the wideband gauge shows a lean reading. It started up and idled fine at 14.7, but under load it read 15-16. By the time I got home and parked, the reading was 18-19. This is confusing though because the exhaust smells rich and the power fc commander didn't give any indication of excessive knock. Could this mean the O2 sensor is bad?

I cleaned the MAF sensor last night to see if that would have any effect and it didn't help.

I have no idea if these problems are related, but let me know what you guys think.