I just bought a SAMUF and it is not exactly clear what parts are US made on it. I know the polymer furniture is US made and I have heard that the hammer and disco are US made (heard that the trigger is Bulgarian).

I don't really care about US parts or any of that - I just want to know if the gas piston and the underfolder stock itself are both Bulgarian made parts. The one thing I cannot stand on imported AK's is the shitty stainless steel gas pistons they usually install.

Typical milled SAM7 rifles only require 5 U.S. made parts vs. 6 for a stamped AK, from what I understand.

On a normal SAM7 the U.S. made parts are as you mentioned - stock, pistol grip, hammer, disconnector, and handguard.  The BCG and piston system are all Bulgarian made.  I know Arsenal USA used to make a FCG for the SAM7 that was all U.S. made so it was the hammer, disconnector, and trigger.  My guess is on the SAM7SF and SAM7UF they have Bulgarian stocks and then the full US made FCG.