Installed rebuilt 302 rated at 340hp

Even with all factory EFI stuff, I thought I would have seen an significant increase in performance. Not so. With the aid of other mechanics, I've upgraded Injectors from the stock 19lb, to 24's. Some change, but still quite sluggish - when compared to stock. Next, I went to an open flow exhaust system: new Cat, muffler, and 3" pipe. Again, some gain, but maybe back to stock numbers. Lastly, I added a 61MM Throttle Body. Once again, some gains, but nothing that I expected. Oh, I almost forgot - I added a BBK pressure regulator and meter. Stock fuel pressure is approximately 37psi; I upped the pressure to 40psi - to compensate for the 24lb Injectors. Occassionally, I'll get a 'check engine' light and code 730 (too rich). Actually, that's when I backed off the fuel pressure from 44 to 40. Now I still get the code 730, but less often. Performance sucks. Sometimes idle gets messed up. Sometimes to the point that the engine quite. Restarts okay, idles okay. Could the MAP be bad? Other ideas?