Mitsubishi Repair: 97 mitsubishi diamante, mitsubishi diamante, mechanic shop

Question
Recently got a tune-up , now my car idles up to 2000 , then in a couple of minutes , will heat up to the red . this problem also is affecting  the way the car shifts gears ,it constantly wants to downshift while at high speeds , or will just occasionally like shift in and out of gear like I have a stick shift .

Answer
Mark,
Your idle speed should be around 1000, and the temp gauge should never reach the red.  Overheating can cause severe internal engine damage.  The downshifting can be an indication of your car trying to prevent more damage by not allowing too high of speeds to be reached.   If you feel the mechanic shop that performed the tune-up may have caused this happen, take it back and have them inspect it.  If it is found they caused damaged, and they are honest, they will fix your problem at no additional charge.  But in any case, have a mechanic check our car to find the problem.  The long you allow this continue, the worse (and more costly) the problem may get.
Good luck!