I was going to do a turbo swap so I had an N/A intake manifold on. I decided not to go through with it so I put the supercharger on. I changed the tune, but for some reason, the tune I loaded wasn't quite right for the car. The IFR was a tad lean and the maf was out of whack. the difference for me was that my car on startup would read +16.4. I thought I had a vacuum, but it was just a tuning issue. I would look for a vacuum leak first, but if you don't find a leak like I couldn't, then maybe some of the cells in your maf need adjustment, and if you have changed injectors, maybe your IFR isn't exactly what it should be for the range when the car goes lean.
