Upgraded CPU in M6600, GPU usage randomly drops to 0% now. AC Adapter the culprit?

I recently purchased a Precision M6600 that included the dual core i7 2620M and the FirePro M8900.

When I game, I run throttlestop to make sure that the CPU is running at its nominal/turbo and not getting stuck in speedstep frequencies.

When I had just the 2620M, gaming was fine for many, many hours. I would never have an issue.

I upgraded the CPU to the quad core i7 2920XM, which has a 20 watt increase in TDP over the 2620M(35W to 55W). Now whenever I game for maybe an hour to 2 hours, my game will randomly drop down to like 2-5 FPS and my GPU usage will go to 0%. I can restart the game and get normal frames again; I assume this is because I'm dropping the load and subsequently the power consumption and then ramping it back up.

I believe the culprit here is that Dell shipped the M6600 with a 180W AC Adapter when the M6600 is supposed to come with a 240W AC Adapter.

Does the issue I described just sound like an AC adapter issue? Temperatures are fine and no throttling is occuring when this happens. I went ahead and called Dell Financial Services to have them send me the proper AC adapter but I was just hoping to get some "peace of mind" before I receive it.

Thanks!