New Injectors

Hi guys I'm new here. I just bought a 1994 Mustang GT with quite a bit done to it. Now I'm not great at motor work by any means. Heres my problem. I changed my injectors to 24# and put in a GMS 75MM MAF. No big deal right? Well my car now runs rough as hell and occassional stalls. I then changed the MAF back to the stock one and the car ran great, had alot more pull than with the 19s but the CEL comes on. I'm assuming its from the O2 sensors. I have since changed everything back to stock since I dont konw if its ok to run 24# injectors and a MAF that isnt calibrated for them. My big question is why would the car run alot better with the stock MAF than with the new one? Do I need to add anything else? I tried adjusting the TB but that didnt seem to help any.

Mods: GT-40Y heads, GT-40 upper and lowers, SVO elbow, FRPP 65mm TB, E303 cam, FRPP Shorties, O/R H pipe, Borla Exhaust, 3.73 gears, Under driven pulleys I believe thats all on the motor

Please any help is greatly appreciated I want to get this up and running before I have to put it away for the winter Thanks guys.

Everything was bought new from Summit Racing. I disconnected the battery negative first then positive for about an hour. I have a feeling that its the MAF I have a friend with a C&L but have to see if he'll let me take it off his car. The GMS is calibrated for 24# and is for the 94 95 model. At least thats what the box says. And to clear up any confusion this is GMS new model not the one with the faulty pigtail, I went rounds with them on the phone over it lol

Ok so my GMS MAF is the faulty piece. We hooked up his Pro-M and it worked just fine. Now I need to take mine back hope they return it and have something else in stock or it looks like I might be looking elsewhere for parts lol. I kinda figured it was the MAF now I'm positive. Also I got the codes pulled and it was 157. MAF not getting enough power or something like that.