I have been working on figuring out my fueling issue for a long time (pressure fluctuation). Also hoping to fix that little stumble everyone talks about, but it was not my goal of everything. I have replaced everything. As for mods, I have a built motor internally, FMIC, 18G turbo, Grimmspeed downpipe, up pipe and boost control solenoid.
More importantly since this is a fueling issue is the fueling mods:
DW 65C fuel pump
DW 740cc injectors
New OEM in tank fuel filter
Replaced fuel pump and filter O rings twice just to be sure they were good
Had injectors cleaned and tested by DW, passed perfectly
I replaced my fuel pressure regulator with a new LGT one from Subaru thinking that was my cause of the fuel pressure fluctuation. Dident help.
I came down to the 1 year old DW fuel pump being faulty and started talking to DW. I read and asked them about something I found online saying when you have fueling mods, especially with there DW pumps that they do not like the bypass style regulator that our LGT's and the 08+STI have. I figured I would try one last thing, and found most people with 08+STI replace there regulator with a standard style one, like Automotive, Tomei, or a older gen regulator off a 07 and older STI. Perrin just came out with a nice regulator but they want $300. I got some quick connects from Amazon, and a STI regulator from Subaru and fuel injection hose from Napa. Installed it all like the Cobb Tuning kit is set up, but they want $290 for there kit (http://www.cobbtuning.com/Subaru-08-...t-p/315100.htm
), and I made this for $140. Not only has it fixed my fuel pressure fluctuation, but the stumble that everyone talks about is completely gone. The car accelerates smoother under WOT, the car drives nicer just going with the flow of traffic and using light throttle, all over better.
Anyone else ever tried this?