We're in the market for a different diesel truck to pull our trailer, and with the changes in motors due to emission requirements, would we better off finding a good, low mileage "pre-emission" truck, or go with the new? For those of you with the new diesels, how has your mileage and power compared to previous models? We've bought new in the past, but I've heard of some disappointment witht the new motors, both in power & mileage. Thanks for your input!