Clean the MAF. Put Heet in gas. Test for plugged cat by removing O2 sensor.
Edit. The best way to test if the exhaust is blocked is to take out the O2 sensor (disconnect battery first), then see if the car drives better. That gives the exhaust a place to exit. Remember to put back the O2 sensor after the test. I think the O2 sensor can be removed with a 22 mm crescent wrench (I used a 7/8 inch crescent wrench when I removed mine to install MILeliminators).
MAF
http://www.contour.org/mods/mods.php?s=howto&displayid=36
