Gary, I installed the rv275's in my truck @ 70kmi and really like them. If you can keep your foot out of it you can gain a little in mileage. I took the Superchips off as it really smokes on any level, and I still have stock clutch. I added an Anti Defueling Device (ADD) from Haisley Machine which lets the boost go over the 18 I was getting. My wife laughed at me the first time she rode after the sticks, "you'll get a ticket now for sure". Needless to say I don't get any better mileage but the grin factor alone is worth it. With our rv in tow the egt's are still ok. Ponz