There's a bunch of possible problems here. Almost anything in the clutch and clutch release system could be at fault, with a few possibilities standing out, like the TOB or the clutch disc going south.

If you got the newer ACT TOB, it shouldn't be that different from a Mitsu OEM tob. The old ones were metal sleeved and could cause a lot of problems up to destroying the tranny input shaft, but the new one is plastic sleeved and similar to OEM.

BTW, was that you calling yesterday? I saw that I got a call from a 5-something area code I've never seen before and a voicemail. I'd have checked the voicemail, but for some reason I have to go through some sort of initial setup to access my box and I didn't have the time.