Hi,

I've got a 98 1500 with a 4.3 5-speed that runs rough when its travelling at a constant RPM, but when I boot it, it smooths out. I recently added a Thrush glasspack, but it was running great until the weather got colder up here in the great frozen part of the Pacific Northwest (Vancouver Island), and it acts kind of like it's lean. It also has a small exhaust leak at the flange between the end of the manifold and the beginning of the exhaust pipe, I'm not sure if that has anything to do with it.

The only other thing I can think of that might be related to this is a part of the emissions system (small black box) had a hose attached to it that has since snapped off. It's an easy fix, just haven't gotten to it.