I HAVE a 97 W-900 KW with a 430-470 detroit, I have heard of a return fuel line fitting, with a bigger opening, suposed to =more HP & mileage, ANYone heard of this ? there was a guy in canada selling them on Ebay last winter, lost the info, , anyone know of a FORUM for detroit ? i did a search but did not find anything ,thanks ...... roger

Bigger opening = lower rail pressure. That's a power loss, not gain. The thing to look for in the lines is 12" downstream you'll find a coupler fitting. It's a one-way valve that's prone to puke the spring and seat. Hard starting, low power, try that first. Good luck...T