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The hookup from the pressure tap at the turbo controls pressure at that point, not down stream of restrictions. So the TBTC and silencer work will help, so would a Viggen IC. These changes will reduce some of the problems.
You need to set the boost in 3rd gear, not in 2nd.
If you connect the MBC downstream of the IC, the boost will be much more solid. You will need to get pressure from near the BPV somehow. And keep the line from there to the MBC short. The heat from the manifold and turbo are a concern with routing. You need a larger hose for that, and remember that a small bore at the pressure tap near the BPV will create a time delay characterised by the volume of the hose and the smalless of the pressure tap.
You will not find perfection. I was there and running fine on cold mid October mornings. I had a MAP resistor mod to move the presure cut a small amount to reduce fuel cuts, my MBC was feed from the TB. I had a 25mm blow off valve connected near the TB and it vented off boost presssure overshoots * . Too bad that I did not get to qualify the whole setup through a winter where MBC's are not fast enough to head off over pressures with these undersized turbo's. 2nd gear was really fast. The boost was very responsive and I think that I could have beaten Viggens through 1st and 2nd gear. First gear, as you now see, can be overpowered. I did not need traction control in 2nd gear. There never was any wheel spin, but there probably was some wheel slip that would have cause TCS to activate if one existed.
So again, perfection is not at hand. You can get close but 1st gear is over powered. A MBC, plus an added air distribution manifold at the TB, plus a metal BPV and a pop-off valve is not aa cheap solution, far more costly than a $40 MBC. So in the end, what is better, a MBC or a modified ECU? Perhaps both as some have done. The stock control system still creates much to much boost lag, and a modified ECU still has some of this characteristic.
* The blowoff valve was modified to be a phuemo-adjustable pop-off valve. The pressure went to the blow-off valve, and to a small pressure regulator. By turning the PR's knob, the pressure applied to the blowoff valve's hose barb could be changed. This allowed the pop-off pressure to be adjusted without changing springs or stacking washers. That was quite neat and it is sleeping in my parts box.
Given the work that you have done, the two other intake mods need to be done. And a Viggen IC will really help as the stock IC is what is holding the system back.
Sorry, no simple answers. Its a quest.
posted by 208.24.17...
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