So I went WOT in 3rd gear today, then went to neutral to slow down. While in N, I noticed the RPM's started fluctuating between ~450 and 1,200 in a fairly steady pattern. My initial thought is that there may be a vacuum leak (or even an ECU issue?), but wanted to hear from anyone else who may have ideas. I didn't notice any fluctuations once I stuck it in 6th.