MBC boost spike
 

I have an Ebay special brass spring and ball manual boost controller, It spikes from 11 psi and settles at 8. I do have an issue with this at all, what I am concerned about is when I downshift from 5th to 3rd, I'll get a 14 psi spike. Is there any explaination to this besides the fact that I am running a shitty boost controller? Is the spring too soft inside it or what?

Do you have a blowoff valve installed? It's very possible that the wastegate just can't open quickly enough. Are you running an internal or external wastegate, and what was it originally calibrated to?

I am running a hks ss and I was tuned with my Turbonetics Evo 38mm. What you are saying about the wastegate not opening fast enough makes sense because I was hammering from 5th to 3rd from a rev match, not allowing my revs to drop or the turbo to spool down. Thank you for your input.

Is it possible to get a smaller spring for your wastegate?

I'm running the smallest (6.5 psi) spring, I'm about to wait it out for a few weeks and get the 9 psi spring and ditch the mbc and call it a day.