Maisonvi
Grass-Roots Vendor
Reading your post again, it's very possible the pump is the issue. The regulator is controlling to 60 at idle and cruise, no reason it should change at WOT. Makes me think the pump isn't keeping up.
Email resonse I got from DW:
"Thanks for contacting DeatschWerks tech support. Also, thanks for the video. I want to clarify that you are using one 300c pump for both the GDI and port injectors? If that is the case then it is possible that you are running out of pump. The drop in pressure seems from the duty cycle being maxed on the pump. It could also be from the FPR. Another thing to note is if you have an adjustable FPR that the higher the pressure the lower the fuel flow. So if you can lower your fuel pressure you will actually increase the flow of the pump. Your fuel system may require 4 bar(58psi), but if not then running it at 3 bar(43.5psi) can help.
The link below if the pump tech for the 300c that will show you how the pump behaves at different pressures. At 60psi the pump is only able to make 298lph. http://www.deatschwerks.com/resources/fuel-pump-tech/dw300c-fuel-pump-tech
If you have any further questions please let me know.
Thanks,"

