Ford Focus RS (MK3)

2016 RS2, original owner...

Just a first post with some content. I was doing a bit of troubleshooting. I swapped back to my stock HPFP(high pressure fuel pump) and fuel Injectors to prove or disprove that all my other parts were working ok. Been struggling with drivability issues with an upgraded XDI HPFP and Injectors setup and a 93 octane tune. (cold start issues, idle surge, too much burbling, and creating lots of soot).

I actually spoke with XDI today, which I probably should have done before swapping back, and it sounds like it's not completely uncommon to have some "too much fuel" issues when running pump gas with this setup. Ultimately I want to run E85 anyway, but wanted to make sure the issues were not related to some other hardware issue vs the pump/injectors. Car is running flawless on the stock HPFP/Injectors.

I wanted to get the 93 tune dialed before switching to E85, but after talking to XDI it sounds like E85 might solve my issues by requiring ~30% more fuel. As I understand it, with pump gas the injectors can't open/close fast enough (pulse width) to keep the fueling right, and still be in spec.