I looked around for quite some time for my '06 2.7L I5. I haven't done anything to it yet, but even with a brand new resonator it still feels wanting. It has a 10' reefer and insulated cargo box by the way. It does OK on the highway, but once you hit the hills the trans downshifts and it's all over. Reminds me of driving my old flatbed 12.7L MB Freightliner with a 45K load! Alright, it wasn't that bad as it can still pass loaded semi's with ease.

There are no chips. Best thing one can do is build a custom cold air intake. I have yet to get the parts, but I've ordered an Amsoil cone filter already, then I can build around the filter once it comes in. With any luck I'll get slightly better mileage. Total cost won't be over $100 Canadian. Otherwise, there's not much else you can do to increase performance. The exhaust is already 2.5" diam, at least that's the size on my I5 engine. I dare not go any bigger as I don't want to loose torque.