how do I tune up the 3.1 L motor?

Check out http://www.gaownersclub.com The Grand Am used the 3100 & 3400 motor. They have knowledgeable people and DIY instructions.

i did a sparkplug / wire change/ ignition module & coil change to get the engine smoother. have you changed the fuel filter? that might help the lack of power.

PROBABLY ONE OF THE THREE COILPACKS IS NOT WORKING

the best why is to change the spark plugs , air filter , fuel filter, ignition wires & pcv.if it still has a miss check your vacuum lines and o2 sensors.

Do a vacuum check. Here is a guide to help trouble-shoot. Here is a good reference for vacuum trouble shooting.......... You should get between 17-22 in. hg. at idle, depending on your elevation above 2000 feet MSL or mean sea level. To perform this test hook vacuum gauge directly to manifold vacuum. 1. Low steady needle usually indicates leaky intake, a leaky vacuum hose, late timing, or incorrect camshaft timing. 2. If reading is 3-8 inches low and fluctuates at that low reading suspect an intake manifold gasket leak at intake port or faulty injector. 3. If the needle has regular drops of about 2-4 in hg. at a steady rate the valves are probably leaking. (Perform a compression check). 4. An irregular drop or down flick of the needle can be caused by a sticking valve or an ignition misfire. 5. A rapid vibration of about four in hg. indicates worn valve guides. 6. Slight fluctuation of one inch or so indicates ignition problems. 7. Large fluctuation perform a compression check. 8. If needle moves slowly through a wide range check for PCV issues. Hope this gives you a good place to start and helps you figure it out.

also clean out your throttle body. Use some carb cleaner and some large pipe cleaners to get all of the carbon build up off of the throttle plate then put some injector cleaner in your fuel tank. this makes a big difference. good luck