starting problem

I have a 99GTP with 47k miles. it has a 3.4 pulley, headers and basic supporting mods. Lately eithor it wont start unless I give it throttle while turning the key, or it will kinda sputter and start up. Also, the lighting in the car will get real dim along with the sputtering until its completely running. It runs/drives great otherwise. I changed the fuel pressure regulator, still the same things happen, I was thinking maby the injectors? Any ideas on whats going on? thanks

Clean the IAC motor and its bore with some carb cleaner.

Then check fuel pressure and make sure its with-in spec. (45psi comes to mind)