 Legally, you're supposed to have all that stuff on there, blah, blah, blah. Disclaimer. Anyways, find a custom tuner that tunes these vehicles. They'll be able to tune it, and it should bring back some of your fuel economy and also give you more power, too, because it's going to be a tuning issue that's going on because the airflow has been altered majorly from factory with that air intake and the exhaust. And that's for a 98 or 99 with a 5.7 in it. If his is a little newer, and he said 6 liter, then you got the LS version, and you can get a little more opportunity to do some things. That's something to be aware of.