99 Silverado

I have a 99 Silverado that seems to run fine until you idle at a light for an extended period of time. It seems to bog down and idle rough and sometimes die all together. There is no check engine light on. It smells like it is running rich when you start it and I had it in the shop for 2 days and picked it up with the guys scratching their heads. Any ideas?

might be pressure regulator on fuel rail but you need to check the fuel pressure or a leaky injector if it smells rick on start up,but you really need to see what the computers reading and doing. is the shop properly equiped and familer with driveability problems.

They said they were'nt reading any codes. Maybe my computer is messing up