Chasing another possible vacuum leak

[TUFTOUR]

Running the NPG turbo kit for many years now. Recently, the car will idle at around 17.0 or so according to my AEM wideband gauge. While driving, wideband goes back down to 15.0 or thereabouts. Nothing seems obviously wrong and I don't find any obvious leaks. At idle, vacuum/boost gauge reads 18. Any ideas where to look that I must be missing?

 

[Beans]

Should be -20 at idle.

If you don't' see anything visually on intake couplers. My next guess would be intake manifold gaskets or PCV between the heads as you can't see that.

But boost leak tester would be fastest, as i can't trouble shoot over the internet.