I have a 1999 Chevy Blazer with 56,000 miles on it. It just got a major face lift. I gave it a tune up, new throttle sensor, radiator drained, fuel system cleaned, intake gasket, the whole nine yards. But after all that, for some reason, the shifitng is rough, especially at 40-45 mph. It seems fine at around 25-30 though. What could be the issue. It wouldn't be bad if it wasn't so noticable. You can really feel it.