Application: Top-Down Solutions tested the stock spring (orange in color) that comes with the GM 17113186 vacuum adjustable fuel pressure regulator (used on GM TBI equipped engines) and found the spring rate was too high. We were unable to adjust the fuel pressure below 18 psi at WOT (Wide-Open Throttle). Swapping this spring for the stock spring (tan in color) that came in the non-adjustable fuel pressure regulator wasn’t acceptable either. This spring was found to be too low of a spring rate. We were unable to adjust this spring beyond 13 psi at WOT. This aftermarket spring is an ideal solution, It is rated at 15.5 lbs/in. and will give you an adjustment range from 12 psi to 20 psi at WOT. The spring is zinc plated to provide years of corrosion protection.