So here is the run down:

Factory turbo, intercooler, piping, mr bov, turboxs mbc.

I have been maxing out at 12-13psi recently so I assumed a boost leak. I checked all the hose clamps and some of them would strip (rusty.) I just replaced all the clamps with new ss ones, checked all the hoses for rips and tears. Nothing. So when I went to drive the boost stayed the same. So my next step was to turn up the boost. I turned it about 4-5 full rotations progressively and during first and second gear it would peak at about 14ish, but would hit 18-19psi in third and fourth. Is that normal?

I turned it up some more and it did not go up, didn't change psi in any gear. So I removed the mbc, rerouted with what I thought was the factory hose and it would boost to 10 psi max. So it's not the factory hose. Is the mbc not doing it's job?

 

What kind of MBC is it? I remember I had a Hallman and I had to swap out the spring.

Also check out the 2 EGR hoses, those are known to pop off.

 

turboxs mbc. one if them did pop off and it spiked like a beast. it scared the **** out of me. spring going bad in it? I couldn't compare it to new since it came with the car when I bought it. I thought about not fooling with it and ordering the factory hose and see if it'll run stock psi.

edit: wait, I thought the egr valve had nothing to do with the turbo? so those hoses wouldn't cause any crazy psi readings...? are you referring to the two hoses to and from the mbc?

 

The EGR is located underneath the intake manifold. You can't really see it, you'll have to reach for it. A disconnected line from it would cause lower boost pressure.

 

Ok so I was looking at some pics of what the stock setup is, and I am way off. The way that the previous owner installed the mbc was wastegate>mbc>turbo. Sounds right since I don't have the factory turbo wastegate actuator, it's gone (now I know what that one harness is for lol.) Looks like it originally was underneath the factory intake, which I don't have either. What should I be looking for in this case? What should be capped of? Somewhere in the intake manifold (egr like you said) and the intake?

 

BTW, It sounds like it is normal. I am supposed to set boost on 3rd and 4th gear. the first two won't hit full boost.

Also, on idle I am only at 10 in Hg. I am roughly 1900ft above sea level so it should be higher, somewhere around 17-18ish? I don't know if the car has cams (checking tomorrow.) CAI wouldn't case this would it?

 

I have the same issue as well. Second gear will not boost past 10 PSI. However, 4rd 5rd can boost up to 20PSI.

Have you found the solution yet ?

Thank you

 

What peak boost level does the turbo hit if you rotate theh MBC adjustment knob all the way out counterclockwise to the softest settiing? Are you seeing 11#?

 

Does your 03 Evo still have the original factory actuator on the turbo? How many miles on the clock?