+1 rebreathing, bringing internal residuals into the intake, due to the timing of valve events, could be something else, but that is when I normally see it.
Good luck
Faster, Faster until the thrill of speed overcomes the fear of death...
71 Swinger - slowly collecting dust/parts 66 Belv. II - just a streetcar 88 Mustang - turbo LS beater
