Join Date: Mar 2010
Location: Ventura County, CA.
First question does it show any type of CEL? At WOT when the car stumbled did the CEL flash and then go away? Any mods done to the car that you know of (tuned maybe)? Have you checked basics like plugs and coils? You said after market fuel pressure regulator, that would make me think of that as the culprit. I don't see why there is a need a for an aftermarket fuel pressure regulator, if the car is not highly modded. I would start there and see. If you really wanna dig deep you can find someone with HP Tuners and datalog it and see what the car is doing at WOT.
2009 Imperial Blue Metallic Cobalt SS/TC Sedan - "Stock":
2008 Victory Red HHR SS - Stock
2005 Chili Pepper Red Ion Redline - Stock
2007 Sunburst Orange Metallic LS Coupe - Sold