piggies are stock downpipes which have the pre-cats gutted and the o2 sensor bung relocated to after the main cat, MBC=manual boost controller. Your ECU controls a boost solenoid valve called the N75, When you run a MBC in parallel with the N75 you can use it to eliminate unwanted boost spikes and smooth out the boost curve. As a solenoid is either open or closed, it sometiomes gives you a spikey boost curve, MBC has a ceramic ball and bleed port which bleeds off air which would be sent to the wastegate to stop the turbo spooling. Thus a much smoother boost curve. Benefits of this setup are that the ECU still controls my boost levels but I have clipped the spike at the top, also when desired I can disconnect the N75 and run the MBC standalone, as long as I am using a TCD=throttle cut defender, I can boost to my turbos uppermost limits*(not advised). Hope that helps clear things up

 

Has anyone gone to a piggyback fuel management system or a standalone? has anyone checked the n75 for any possible restrictions in the valve that can be removed. for an example, in the 1st gen DSM's there is a plastic restictor in the boost sontrol solenoid valve that when removed adds an additional 2-3 psi of boost. Can anyone tell me where the n75 is so that In may look also?