Air/Fuel Guage Question

[Rockman18]

When I bought my Trinity from it's previous owner he told me to not run my truck in the economy mode without running a separate air/fuel monitor because he knew guys that were having issues and messing up there engines. Has anyone heard the same thing or experienced this issue themselves. I was looking at getting a monitor but the wide band ones are more expensive than I realized and wasn't sure if it was really needed or not before I went and forked out the cash.

[mikel]

what kind of vehicle are we talking about here?
There is nothing unsafe about any of our tunes when used on a stock/stockish vehicle.

[Rockman18]

I have an '04 GMC Sierra 2500 HD. I thought it sounded odd but he was pretty convincing so I thought that I would ask

[mikel]

gas or diesel?

[Rockman18]

Gas 6.0L

[mikel]

definitely nothing to worry about....