When it comes to making a lot of the power, one of the biggest set backs you will have is the exhaust vanos. With the fuel pumps being on the exhaust cam it sets a lot of strain and load on the cam itself so it makes it hard for vanos to make any adjustments. It takes a lot of oil pressure to do so but even if you decrease rail pressure to up oil pressure its still not enough to really meet exhaust vanos advance target. 

Without this modification the exhaust vanos will retard cam timing causing a huge loss of power by 250hp and it is proven to do so. This will essentially delete the exhaust vanos so tuning is required. Most high end tuners such as Steven from Wedge, Mike Botti, GTP, Chris from Motiv are familiar with this tuning strategy. Shouldn't be an issue with those guys. 

Over 45psi is where we generally see this being an issue. depending on the turbo

Will require core, we might have some on hand so don't hesitate to contact us first.