So I drove the evo today and my boost is going crazy spiking and i hit fuel cut at times. I pulled over and check the Hallman and it was fine, as far as i can see no leaks or anything, boost gauge connections are fine as well. Since I had the engine built and broken in, I have not moved the MBC, its set at 20-21lbs but whenever I got off the gas, it looks like it the boost jumps up for a sec and then goes to full vacum. I know that the colder temps may cause boost spikes (pretty cool he in CFL), but this seems excessive. Any thoughts on the fuel cut issue and/or the car boosting for a sec when i let off the gas?

I have a Defi gauge and the Hallman is connected from the wastegate nipple to the intake manifold with a JDM MR BOV.

 

why dont you try putting the stock BOV back on and see if that fixes it. If your BOV isn't opening properly or opening at all, that would definitely cause some compressor surge and spikes...

check all connections

 

I swap out the BOV when I get home tonight, and check the hoses.

Thx

 

I highly doubt it's the BOV. It sounds exactly like what happens when the wastegate and pressure source lines are backwards. You said you hadn't changed the MBC connections since before the engine rebuild, though, so that's weird. Double-check to make sure the 2 vaccuum lines aren't backwards. I made this exact mistake when I first installed the Hallman and experienced the same symptoms, fwiw.

 

I checked the direction of the lines and its correct i havnt moved it since in like about 2000 miles ago. Boost has been rock solid until now. I am wondering if its something internal with the MBC. I am gonna try and find another one that I have and try it as well.

 

you might want to check for a leak on the intake side. you might want to try connecting the mbc directly to the turbo outlet.