old school tuner trick to richen up the mix at the top end
You don't need to get defensive you're going to hit hurdles when modding your car it is frustrating but all part of it
did you ever resolve your fuel pressure reg issue? did you end up getting an adjustable one ?
as for the 3-4k for a tune a second hand Power fc is 8-900 dollars and a tune anywhere from 600 upwards from what i've seen this would net you decent gains and the car would probably run better then factory
a nistune even less look DVSJEZ up on here from memory he had a nistune and tune deal going for under 2 grand
when we chatted your car had 300k kilometers on it what's the condition of your timing belt like has the car had the major service done on it
clean the injectors and check the CAS if that doesn't resolve it i would seriously consider taking it to a workshop something else is wrong is your AFM in decent condition ?
Have you changed the fuel filter?