if you are not going to change your internals, and only going to run 13 lbs of boost, just get a s-afc, and save yourself the headache. there is a LOT of stuff that goes on in the fac. ecu (emmisions crap, ignition control, fuel control, and other functions) that is pretty necessary for daily driving. I would reccomend using a stand alone computer if you are building a "race car" something that is NOT street driven AT ALL. even Hahn uses the Accel DFI as a piggyback on teh stage 5 kits. the ignition is mainly controlled by the ecu, with a little help from an ignition amp. With stock internals, and 13 psi, you really won't see much benefit using a stand alone. our map sensor goes from 0to 5 volts at -15in. hg to around 7 psi (not exactly sure if it is -15 or -30 'though). the voltage is linear with the pressure as far as I know. putting a bigger map sensor on it would mess up the fac. fuel curve. I explained this to Murix a few days ago, but this is basically how I see it. Most all MAP sensors are 0 to 5 volts. if you put a 3 bar map sensor (reads -15in.hg. to 30 psi) then it won't hit 5v until 30 psi. So at....say.....15 psi, your computer would be getting a voltage that it normally gets when it is around 2 psi, and would mix the fuel according to that (which is not a lot). and usign a vpc isnt' the answer because it's main purpose is to eliminate the MAF sensor (which is a BIG restriction on most cars). we dont' have a MAF sensor, therefore we don't need it. even if it would work. the s-afc and bigger injectors will do the trick in most average turbo setups.

Have fun!