I seriously doubt all injectors would go bad at the same time.....if you get the same reading for all, I would guess they are ok.....
As mentioned, I would clean the MAF sensor with MAF cleaner......
Is your air filter OK?
Have you checked for vac leaks?
I assume your long term fuel trims are out of spec?
After cleaning the MAF, reset your fuel trims with the Tech II, and clear code ......run vehicle, and then take a snapshot of fuel trim and Pre O2 data......does O2 go lean, causing fuel trim to go rich?
If it does, disconnect the MAF, rest trims, clear codes if any.... and take another snapshot.....a MAF code will set, but does the O2 data still go lean?