If you're only shooting for low to mid 400's you can just use the stock ECU. No need for a piggyback. New MAF sensor and Osiris, you can bring the car here since we're the closest shop to you (still working on getting more mid-west and east coast Pro Tuners). You'll regain stock like driveability and civility and with Cipher you can check your stock sensors at any time.
Obviously we can't do a "flash" for FI cars, but we can tune the car here and you can always send us logs if you need anything adjusted when you get back home. Even with a drive down here, tuning time, software, MAF and anything else you might want/need done we'd be less expensive than the HKS and you'd retain all the stock sensors and controls for reliability.
Just an option.