Lacks power when hot, Bad head gasket(s)?

[Otto]

So after driving about 20 or so kms my truck starts to run like it's doing the robot. It runs pretty emaculate at the right tempurate(about 15 minutes after drive). When it's hot it feels like bad compression, lower acceleration and will slip a lot at lower speeds. I'm wondering if this is from shrinking/expanding old head gasket that needs replacement. I Checked the coolant as well, theres some bits and pieces of black carbony junk that best guess is pieces off the old head gasket(s). How much does a compression check cost? I could buy the guage and Crappy tire for 50 bucks.