I've been noticing over the past few months that whenever I would enter lift (~6200rpm) in my Matrix that sometimes it would only creep up to the redline and not go flying up. This has been pretty intermittent and has not thrown any check engine lights. Sometimes I would still get the expected surge of acceleration for weeks at a time only to have it go slowly for a day or so. I found a forum thread here describing a similar issue but on a Lotus. The video linked in the first post shows exactly what I've been seeing. In the comments, he talked about cleaning the MAF and seeing the problem go away. I decided to do that, and I found that the sensor on the MAF was coated in gunk. A few shots of sensor cleaner later and it was looking like new. I went for a test drive and found that the changeover from small cam to big cam was much smoother and the power was much more consistent according to the butt-dyno. I've got some data to sort through and I'll see if there's anything noticeable in the graphs.