ST215 turbo/wastegate question

So, I have hat the 215 engine running in my ST165 for 3 or 4 years now. Everything has been great and the only thing I have done is add a MBC and was running it at about 12 PSI.

In the last month I noticed I was spiking on boost. I would see it get up to 18 PSI than would take my foot off the gas as I have read anything over 13 is bad and pointless, efficiency wise.

I took my cheap MBC apart and all seemed well with it. So, I "think" my wastegate may not be opening, or atleast not opening quick enough. What is the best way to verify this? Can I just cap off the waste gate actuator?

The diaphragm could be bad. . To test, connect a vacuum pump to the actuator and see if you can build a vacuum.

Looks like this, you can probably rent one like this from an auto parts store.

I've used a bicycle pump before to see if the wastegate arm moves. Just have to be careful to not put too much pressure in it. Should open around 8 psi.

Thanks for the ideas. I will try and remember those if I have a real issue.

Turns out, the vacuum cap I placed over the unused port on the actuator had popped. This is the port you have to cover when going MBC and I forgot all about it till I was looking at the actuator and saw cracking on the cap. So, it was leaking out of there.

Thanks for the help and gained knowledge!!