V70 R boost too high / boost too low codes

[matthew1]

P0299 Low Boost Pressure and P0234 Engine Overboost Condition, confirmed by Dave at Volvo Specialists two days ago on VIDA. He did a quick VIDA download. These are triggering a Check Engine light. It has a new Turbo Control Valve Part# 30670449, so that's not it. No vacuum leaks that I could see after taking the airbox off and mucking around.

On Dave's suggestion I took the MAF off and gave it a few good blasts of MAF cleaner. Haven't tried it yet, I'm letting the MAF dry.

I can feel the computer applying/cutting boost in and out during full-throttle. It's a subtle on/off feeling, and during shifts or when I take my foot off the gas there's a squeak or chirp from (I'm getting more and more sure) beneath the hood. At first I thought it was the front wheels chirping from too much spin after catching the next gear, or much worse, I thought it was the back wheels pushing the fronts on gear changes. But like I mentioned, I'm starting to think it's the sound of air escaping from the boost maze under the hood.

I think this condition was exposed after the 90k service woke the engine up.

Any ideas?

[JRL]

Short of a complete failure with the wastegate your problem DOES sound like the BCV
Just because you installed a new one may mean;
1: it was installed incorrectly or
2: you bought a bad one

[matthew1]

It was installed incorrectly. Two of the three vacuum lines were in each other's spot. She runs like greased lightning now. Thanks JRL.