problems with new motor

Okay so at 144k the DOHC in my 97 slduece decided to spin a rod bearing and destroy itself. I managed to find a good used motor at a local salvage yard for 500 bux with 111k on the clock. My car has a manual trans, the donor car was a slush stick. Anydangway, we put the new motor in and the car ran fine. For about a day. Now the motor has a tendancy to run much hotter than the previous one ever did. Not overheat... just runs hot. The old motor usually stayed right above the 1/4 tick mark on the guage, while this new motor runs with the needle normally a little to the right of halfway, unless i'm on the freeway where the temp is usually between the 1/4 and half marks. Now this wouldn't really bother me except once the car is hot, it doesn't seem to run right. It won't pull at all, like there's no power. I've replaced the thermostat but no dice. Still hot. When we had the car apart I gutted the cat. Would this have something to do with the car running too hot? The service engine soon light has been on since the swap as well. Is there a possibility that something is clogging the exhaust? I'm stumped and it's starting to piss me off cause that car used to be quick. Now I'm getting spanked by punks in their mom's 4 door civic and I can't take much more of this.

what was the year of the junkyard motor?

depending on the year, you'll need to replace the ECT.

you should also check the forums over at saturnfans.com