You are right about the standard injectors being about the limit for 300 bhp, but I think to achieve this the fuel pressure has to be upped otherwise at standard pressure you are limited to about 270 bhp.

I'm really trying to figure out what the limitations of the eec-iv system is, changing things like the MAF, injectors, MAP sensor, disabling EGR etc are all possible but somewhere along the line I suspect that the eec-iv won't be able to respond to any further mods.

Taking for example Azrael's post from farther up the thread, he said he couldn't find anyone to map for a different turbo. From what I've seen to date the eec-iv code doesn't know what turbo is there (or need to know), as long as the sensors can measure whats happening, the injectors are up to it and the calibration tables suit the extra air flow the eec-iv should cope fine. Who knows though, I may be wrong, but there are plenty of V8's stateside that have had turbos and superchargers fitted and they chip their eec's to alter the tables and get a useable daily driver with more power and torque than we could ever dream about.