I had a similar problem, I never put my car on the dyno before I flashed mine (which I should have done), I just had the generic 10psi tune and went for a dyno run, flashing the car that morning on the dyno it made 167rwkw on 10psi, then 162rwkw on 8psi and back up to 165rwkw on stock tune. With the boost guage saying that it was pretty much on the money for all boost levels for each tune. And driving the car showed that the boost seem to come on late. At that stage I was working as a mechanic for ford. So come monday I went to work and checked all the hoses for incorrect fitment or splits and holes as well as intake and exhaust manifold bolts (which I had done the day before the dyno run and all ok. Hooked up the PDS (diagnostic tool) and it was throwing a wastegate fault code, I cant remember the exact one. Which I thought was strange as I thought if it was a wastegate issue it would either boost off its eyeballs it wastedgate was stuck closed or not boost at all or very little if open. so I checked the wastegate plumbing and the control solenoid, all tested ok, used a mitevac to test the pressure required to be applied to the diapragm to open the wastegate, and again all ok. So I cleared the code from the PCM and took the car for a drive, and the all of a sudden I had my old car back. I suspected that the wastegate solenoid was being commanded by the pcm so open too early and causing the wastegate to open early as well and hence take too long to boost, but still be closed enough generate boost in higher rpm and load to register correctly on the guage, although I haven't had much time to tinker with faulty turbo's and control systems as being a ford dealership I never go to see many highly midified xr turbos. I rang chris romano as for some advice and he seems to think I downloaded the tune incorrectly and had caused the vehicle to log the fault code. But Ive flashed it backwards and forwards previously with no problem. Ive run a self test since then with the 10psi tune still in and no fault code present and the car still goes as it should. Now if anyone knows more about the flashing process let me know, but I know when you reflash a ba-bf with the pds uploading the regular software updates that ford releases, after each reprogram, it clears all DTC's (diagnostic trouble codes), so I wonder if the tune boxs carry out the same procedure, but if this was the case then the fault code would have been erased when I flashed it to another tune on the dyno, assuming that the condition that caused the fault in the first place wasn't still present, but like is said there wasn't anythig wrong. I know that when flashing sometimes you can get corrupted data although the design of the CAN BUS network is suppose to reduce that. So If anyone else has any ideas as to wtf happened please let me know. I plan to make the six hour road trip down to the dyno day at elite automotive next month so I will suss out paul then about the issue and about a tune after the injectors, springs, pump and hopefully a process west cooler and plenum kit. cheers Mic