Just hook a line from your Waste gate directly to the comp outlet and see if you make gate boost only, your Hallman may have the spring or ball jammed, remove it and rebuild/clean/lubricate it, also replace your vac lines with fresh while you are at it, they could have a micro split that is letting pressure blow through when stressed preventing psi getting to gate.
FYR - boost cut is usually set a couple of psi above your target, depending on your tune/wastegate % demands, you may well spike from time to time, this is ignored by the ECU IF it is a low enough level and a REASONABLE amount of time lapse.
Colder weather will make more boost due to air density and will create more engine load, with a MBC you have no ECU comps working for you, bear in mind also that giving it a foot full from low RPM will build boost spikes easier, taller gears will also induce overshoot/boost cut if not dialed correctly.
MBC have their place, I have used lots of them, also used and tuned 2 port/3 port and hybrid boost control configs, my last Vehicle I ran a 19.99 mbc as it suited my 'bang for buck' project at the time. Hallman make a good MBC but I have had to rebuild my own previously.
Last edited by Kastley85891; 12-30-2012 at 02:33 PM..