I had the same thoughts of installing one on my 250 engine. After talking with a few shops, they all said the same thing, the engine must be kept in tune very close to perfect or you will melt it down.
My solution was to install a AIR / FUEL ratio gauge. It uses a O2s in the exhaust to read the ratio. After a few weeks of tuning and a handful of different metering rods, I was able to eliminate 90% of the smelly exhaust, increase fuel mileage, and make for much better driving truck. I went from 14 - 15 mpg to 20-21 out on the highway, and that's at 65 mph! I will bet money, your running rich and needs more timing.
Joe
