Does not look like a normal graph to me though. Makes me wonder what is really going on. The torque seems extremely low and there is no way the thing is out of fuel at 3,500 rpm due to the injectors. My L31 made 185 whp and 250 wtq stock on a Mustang dyno. On a dynojet it would have made the normal ~200 whp. After the GM 6395 cam, 1.6 rockers, tri-headers and tuning it made 229 whp and 304 wtq with bad valve float. I had also switched from the 4L60E and 10 bolt to the 4L85E and 9.5 SF rear axle by that point. I swapped the springs out for Pac 1218s and put Comp 787 retainers on it. Power increased to 257 whp and 310 wtq and the curve was much smoother. At that power level, I switched to E85 and still had some headroom injector wise. On E85 it went to 272 whp and 330 wtq. The stock spider fed my 383 up to 5,200 rpm before it ran out of fuel. At 5,200 my 383 is making ~470 hp at the crank, which is why I said the stock spider is easily capable of 400-450 hp.
I also do not understand why a performance shop could not do any work on a non-LS. Unless the wiring for the 02 sensor was removed, adding an 02 sensor past the collector and plugging it in, is not rocket science.
2-bar MAP sensor needs the correct custom operating system programmed into the computer, but both HP Tuners and EFI Live have that setup as an easy upgrade to do.
The wiring for the MAP and 02 sensors is the same as a LS.
Seems more or less they just did not want to mess with it. Like most shops that call themself tuning shops, probably copy paste basic LS tunes that are close into the PCM, adjust the power enrichment multiplier and call it good. They can turn that kind of tuning around in 1-2 hours and 3-4 dyno pulls. Then they give the vehicle back to the customer, the customer floors the vehicle pulling away and it sets them back in the seat more and they are happy for a couple days until they start noticing all the driveability flaws.
