generally the chips offered are intended to work with factory computer 2 alter factory fuel maps makeing it more suitable for aftermarket cam profiles.
with the aftermarket fuel injection system you have it really wouldnt be a benefit do to your fuel system haveing a stand alone program system. you'd be better off with an adjustable fuel regulator to further enhance your holley system if not allready installed and plug and play with a lap top 4 the pro-jection. also makeing small increment adjustments 2 your timeing and possibely useing retard function for high RPM adjustment 2 free up further power regardless of if not haveing a power adder.
The chips are suposed to be custom. If they know about the systems they should be able to tune it for you. I've considered a chip myself. I don't know about diablo and Mustangs but I know it made a world of difference in my friends' modded OBDII vehicles as far as drivability is concerened.
the holley pro-jections fuel maps are intended 2 be adjusted via a lap top computer giveing the tuner easily accesability custom features compared to the oem's limited chip method.
it is a nice system that dosen't relie on factory computer useing some of the oem sensors functions for feedback.
i currently run a pro-jection setup allready installed when i purchased the vehicle on my 68 camaro and am quite pleased with it.
regardless of application, if it's an aftermarket holley pro-jection unit you are useing, it is adjustable without haveing to alter factory computer with laptop.
ok your sig threw me. its really up 2 you on the probe, wether the minimal power gains from a chip will be worth the cost of the chip. if it was for a V8 with heavy mods i would spend the money for the chip in my opinion due to seeing better power increases. for a relatively stock motor 4cyl. or 6 cyl. probe 10 to 20HP if even that might not be worth the amount of money 2 aquire it to me.