Alright so my cars been acting up a little lately. Just have a few questions.

91 RS

I get some blue smoke when i take it past about 4k RPMs and get on the gas.
I know its oil, but what can fix that?

There's also a rattle underneath which seems like its coming from the catalytic converter? Heat shield maybe? only at 2k RPMs does it rattle.

Also I think I might need a new thermostat. We just replaced a tiny hose because the old one was destroyed spraying coolant everywhere. We did the flush now and seems to run fine, levels are fine. But during long drives the temp shows to HOT and the heater blows cold. It seems to go back down after turning the heat off and basically I have to do that everything 30 or so minutes.

Anybody here to help?

 

could be ur piston rings or valves seals.

see if the 10m bolts are loose on ur heat shield.

and check if ur fan is working.

 

Alright I'll have to check on the bolts tomorrow.
How would I go about checking the piston rings or valve seals?

I'm pretty sure teh fan works, I'll have to check on that too