when was your last tune up? my truck would do the same...when i pulled up to a red light or even got under 20 mph my rpms would drop and struggle to stay running and it stalled once, its an automatic btw....took it to the shop for a tune up at 182,000 miles and the guy said it was the first tune up! i bought the truck at 175 k...couldnt believe the guy was so cheap to never get a tune up...runs good now