Blown headgasket?

[Green7mgte]

the HG is defective from the factory. too low torque specs.
do you have milky looking oil on your dipstick? do you have oil in your overflow? those are signs of a BHG. tons of info on what to look for in the faq, give it a browse.

The bubbles behind the dash is air in your heater core. The heater core is located behind the dash and is lower then your rad cap. so air will travel through the system and collect in the HC making that waterfall sound you hear. all other issues aside if you jack the front end up and remove the rad cap and let the car warm up for 15 minutes adding fluid it will "burp" your coolant system. also covered in the FAQ (or it should be)
as for your gasket kit. just get the one for the 7mgte.
Good luck man.

http://www.toyota-supra.info/forums/...-symptoms.html