Lately my car seems to be boosting a little high. I see 1.3 blip on the stock Gauge for a second before it drops down and stays at 1.1 - 1.2

I can lower the boost build by loosening my wastegates.

The question I have is that sometimes, in 4th and higher, the car seems to stutter under WOT right around 5,000 RPM. Almost like it's hitting a soft rev limiter. The revs continue to rise, but there is a definite slowdown in acceleration.

Does this sound like plugs? they are about 12,000 miles.

 

I had a similar problem under WOT at 4500 RPM. Basically it felt like I let off the gas for a very brief moment, then it kicked back in. New plugs solved the problem.