RNM, yes, but 14-15 is lower than the stock taper.

 

i boosted again today and it gave me 12-13 PSI at 5500 rpm. Do you guys think is the MBC problem ? Someone really need to help me out please.

 

Well you don't even know what brand your MBC is, so there's not much we can do. How do you have a IX, yet you don't know what MBC you have? Didn't you buy it? We need to know what it is, and we need to know your other mods. If you have some generic old MBC, it may just suck. You could also have boost leaks. You could have done a poor install on the MBC. There are so many possibilities, but all you're telling us is your boost is low and to "help me out please."