1986 Subaru XT 86 Subaru XT turbo

I've posted once but did not recieve a response. My car, the subaru xt, has been having engine problems. I would drive about 3 -4 miles then it would start lose power, like I was letting go of the gas and eventually kick back. Ive check the coolant temp sensor, changed oil filter, fuel filter. So originally I would turned the car off while it was moving and turn it back on then it was fine, but now the second the car hits normal running temp it does this and the only thing I can do is stop turn it off and let it cool. Im confused. Is ita temp sensor or ssomething else. Ive also changed out the catalytic converter but that did help either. Please help me! -Jesse