I have a 99 s70 turbo. Running very bad "limp mode""and shows a misfire code on Cylinders 2 and 3. also oil in cylinders 2 and 3.

Seems to have substantial pressure in expansion tank from startup.

Was told when recently purchased that it needed a head gasket.but i'm not sure

 

did you inspect the intake tubing? its possible that your PCV oil separator has failed and oil is getting sucked into the intake. As to pressure in the cooling system - does the upper radiator hose swell and appear overly firm? a pressure test of the cooling system would confirm, plus you can buy a $40 kit to check for HC's in the coolant (ie the exhaust gas is leaking past the head gasket and pressurizing the cooling system. This will also put unburnt fuel in the coolant which is what the kit will detect.