Originally Posted by
rmcdaniel12
By all means correct me if im wrong, but I would assume that may be the case for a stock fuel setup with the internal regulated filter, but wouldnt that be different with the external aem regulator? The regulator is designed for that. Also makes me wonder if thats why members with 550cc injectors are having trouble running rich at low rpms because they are increasing the fuel pressure to compensate WOT. With no vacuum, the regulator is still dumping at that same psi at lower rpms. With the vacuum line installed to the regulator, this would allow for Robs suggestion of 56psi for idle, and when in boost the regulator will self adjust accordingly.
The regulator may be designed to run fixed or vacuum referenced fuel pressure, but the TUNE is written for fixed (fixed relative to atmosphere) fuel pressure. A tuner could probably create you a tune for boost/vacuum referenced fuel pressure, but that is not how the stock tune or canned tunes are.