So in the past I have been against running E85 on the factory Jbody ECU. I know a small handful have done it fairly successfully. I was really against how it has been done. Using a fake injector constant to trick the ECU into adding more fuel. Because of this I would not try.
This past year after dealing with some of my own tuning issues and injector issues. I came up with a idea of trying E85. I wanted to prove if it could be done successfully, but also without faking the ECU.
Because I did not have enough injectors and not having E85 all around me in my area. I decided to try E47. Also research shows that the possible HP difference between the 2 are minimal.
So my car has been running on the GM LD9 reflash for years. I'm running 60lb injectors. I left my injector constant alone. I used the injector pulse width multiplier to add my roughly 10% more fuel to my tune. I started with adding 8% and after some driving and watching my fuel trims I had to add a little more. Close to 10%. Then just some fine tuning of the VE tables. I dynoed the car this past Friday. Same Dynojet I have used for years. Gaines 19whp and and 23wtq. Final numbers of 241whp and 259wtq. Only changes to this setup from last dyno was Different injectors (went from 80's to 60's because of a sealing issues). I have not had the chance to figure out my gas mileage yet. It appears cruising it is not far off, but under WOT she drinks. I'm maxing out the 60's on this setup.
I still have some fine tuning to do on the cruising part (need to fix my exhaust leak first).
I will say I was wrong in the past and you can do it. The way I did it I feel is the best way, but I also know that the IPW table is not available for all years. I believe 99 is the first year with that table. I did have a cold start issue at first, but have been able to tune that out.