Wide band on the dyno. That is a quick way to find out what is happening. First put the stock stuff on the mustang and make sure it is tuned up. This may take some money but will save you in the long run. Then Decide if you want to put a lot of time and money into it or just drive it for mpg. either way you can find out some on the dyno on A/F and what is wrong if anything is. I found a bent valve and a bad fuel pressure regulator on mine. Best money I every spent was wide band and Buying Matt dinner!
Make a plan and stick with it.

Yep. :D

Unless you are running or going to run a power adder turbo, blower etc it is best just to leave it stock....:jester:

well like svobrown said make a plan and stick with it I did , so until i can get a donor car for a it will stay a 2.3