How did you check for vacuum leaks? The best way I have found is to lightly spritz carb cleaner around all the areas that can leak and listen for the engine rpm to spike. Gotta check all the vacuum hoses, the throttle body, the intake gaskets at the heads (known to leak on these motors), and all the air intake between the throttle body and Maf sensor.
If you are confident you don't ahve any vacuum leaks and the wiring is good you really need access to either a scan tool that can read real time data to check MAF hertz or a DMM that can read frequency. If you go the DMM route this is a good tutorial on how to do it.
http://easyautodiagnostics.com/gm/3....sensor-tests-1