I'm wondering if there is a temp issue. It hasn't been hot out, but, the factory gauge barely moves, and the heat is never really hot (even the hoses to/from the heater are just 'warm') no matter how long its running.

If it is indeed running cold, my short (5 mile) commute to work sure ain't going to get it fully up to temp.

As for the catalytic convertor, when I bought the truck, there were two installed inline, the original one, and back where the stock muffler was supposed to be, another one. The new one was less than two months old, so, when I had a stock muffler installed, I had the shop replace the old stocker with the new one already on the truck (moved it from the back up to the stock location).

I know this thing will never be a Neon in terms of MPG, but, single digits is unacceptable.

Grizzly.....shuddap.