I have a customer that brought in a unfinished 383/Whipple project started by another business. The other shop built the engine and installed the Whipple but got lost when it came time for the wiring and fuel conversion. I reluctantly took on the project, finish it and put it on the dyno only to find out the IAC does not work in the computer (Merc with Whipple tune) and the fuel tables are way to rich. The first pic shows it with the 50 lbs fuel pressure that the instructions want and the second pic is with it down to 30 lbs (still to rich). We are wits end and I might have the owner convinced to go with the Holley computer system. The only concern I have is the Whipple has a Ford 2 wire IAC and I didn't see where that as an option with the Holley EFI. Any other options?

The Holley harness uses a 4 wire for the IAC. I use this P/N for the IAC, GM 17113099. I run this on a whipple 540 with Holley HP.

Looks like you can use numerous IAC formats in the Holley, in your case you might have to massage the Harness a little bit.

I guess I should have turned on my Holley program and looked instead of their online site.