im having the same problem i have tbe hallman mbc apexi intake i hooked this up 2 different ways wastegate to turbo and wastegate to intake manifold to bov T bov line used new hoses and the same thing i pm some people they said has something to do with your wastegate?? i dont know i never had this problem with my 8 cold weather never caused to go up and up around 5500 rpm it starts going up 21 22 23

 

wastegate dude. I think. it makes sense in my head anyways.

 

I'm in the market for a MBC myself and did some research and found something interesting from a Turbonetics dealer. Their MBC claims to be more reliable than the typical ball & spring type which can cause boost spike/drop. Sometimes in hot weather the spring & ball tend to expand and in cold weather stiffen up (which sounds like whate your MBCs are doing during these cold winter days). The Turbonetics (which looks just like the HKS) utilizes a Acetal/Nitrile Diaphragm eliminating the sticking problem of the ball/spring type. Not bashing or pushing any of these companys, just letting you know what I found in my search. I'm personally still trying to decide which is the best...hope this helps

 

Also a quote from Jamie@WORKS

"External controllers: Some engine tuners don’t even bother to attempt to control the boost with the software. They dismiss this function as being unreliable. We look at it as taking the easy way out. Every manual boost controller we’ve tested still tapers—and changes the target boost depending on the weather condition. While most electronic boost controllers can do agood job at controlling boost, why would you spend an exorbitant amount of money and time setting up an additional electronic boost controller when your EVO is already equipped with one from the factory? (FYI, if you are running an add-on “piggyback” computer or controller, you cannot use the factory boost control because the ECU has no idea of the actual boost level at any given time. Since the piggyback is altering the Volume Air Flow signal being sent to the ECU, the ECU cannot determine how much air is actually entering the system and therefore cannot control boost among other things.)"

 

I'm also surprised that not even after driving my car for a while with the boost controller mounted just to the left of my intake heat sheild that it doesn't warm up a little.

But, the weather was a little warmer out today and I had previously turned my mbc down "10 clicks" to about 17 psi. It did actually hold all the way to redline with a little spike to 18psi early in the range.

Whatever. Can't find a simple solution to cold weather. It would be nice because the car feels real quick.