Hi I have a 02 bugeye hybrid with vf39, grimmspeed ebcs, and all supporting mods. I have been boosting 19psi at 11.4:1 AFR with no problems. Then all of a sudden one day I was getting on the freeway and I hit on it and it stuttered for a second and then kept going (19psi). Well I get off the freeway and boosted it in first, right when the boost was getting over 10psi the pressure started going all crazy like 13psi, 17, 15, 18, 14, 19. And my AFR's went down to 10:1. Also the motor started stuttering and was kind of shaking (and it was back firing from going so rich). Then I let off and the car drove fine as long as I dont go over 10psi. I tried the same thing in second gear and it did the same exact thing. I did a 20psi boost leak test and heard no leaks. I took off the TMIC tightened all the clamps, checked all the couplers/gaskets and found nothing.

What do you guys think it could be?

Thanks
Eric