96 GMC k1500 Suburban with a 350. I took off my throttle body and cleaned it with carb cleaner. It had about a 1/4 inch of gunk underneath the butterfly. Got it shiny clean. I replaced the throttle body gasket on the intake too. I have 1000 rpms at idle in gear, but when driving, the idle doesn't drop back down right away when I let off the gas. I believe the idle is supposed to be around 800 rpms? Any advice? Thanks.