If you're showing 2000 rpm now at 70 mph, and with the tune you were showing the same rpm (2000) at 80 mph, your Tire Size (TS) is probably set too high in the tuned state, or, you have non-OEM tires on the truck and since you are runnig the "stock" tune now, your PCM "thinks" your tires are smaller than they actually are. So, with your lift, did you install bigger feet?
If so, your engine has to work harder than before to maintain that 2000 RPM in 4th gear with the Torque Converter locked. That will be noticed as an increase in engine sound.
And, since you have a 2004 truck, you may really need to clean the throttle body (and possibly the MAF sensor). Your symptoms sound like that could be the case and the problem is aggravated by custom tunes. I'd certainly pull the air cleaner housing and have a look at the throttle body. If if looks "gunky", clean it. Bill writes about this problem here:
Power Hungry Performance - Frequently Asked Questions It's the first FAQ after "FAQs about Everything Else".
- Jack
Mon, September 27th, 2010, 04:17 PM
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