Sooooo...I had a nearly perfectly tuned and running 350 TBI conversion in my Malibu station wagon and decided I needed a 383. My plan was that a good starting point would be to take my previous tune and make some changes to it that should bring it in the ballpark so I could get started down the right path with my 383, since it was not all that different other than the displacement. The 350 had a stock sized TBI and stock 350 injectors running at 18 PSI, the BPW was set to 115 and all worked great. Based upon the new displacement and a change to a bored 454 sized throttle body with 70lb 454 injectors run at the higher 18 PSI I calculated a new BPW of 86. It seemed to actually run OK just driving it around but was pulling tons of fuel with BLMs under 100. I was able to get the BLMs into a reasonable range by pulling a bunch of fuel out of it, and I am sure I could get them perfect if I kept working with it. However as soon as I step down on it and it goes into PE mode it falls flat on its face, pings and runs like crap so I am wondering if my original BPW calculation was way off. No point in continuing to work with this fueling map if I am going to need to start over. Suggestions?