This is a follow up to my other question.
Now the problem is sometimes when inserting a USB stick, the computer freezes and goes to a complete gray screen(kernel panic). It seems to only happen if the USB is plugged in after it boots up.
It has been through two AHT runs, first run through was not extended and it gave only the error
4SNS/1/40000001: ID0R-0.000, which according to here that means a problem with an electrical sensor for DC power. That site recommended to reset SMC, so after that, another AHT was run, this time extended, and it gave the only error
4SNS/1/C0000008: TPCD-- 124 which apparently is a temperature sensor for the power bus.
I'm not sure what those would have to do with plugging in a USB though, maybe they could be related, idk.
Here is a kernel panic log right after an USB insertion http://pastebin.com/q3LWSWbS. Which I believe pretty clearly says it was indeed the USB that was problematic on line #33
32. Kernel Extensions in backtrace: