I think they are worth it. If you drove the car, you would be amazed at how seamlessly the turbo kicks in. I cannot even tell you when it begins to build boost because it's so smooth.
The passages before and after the Extrude Honing is really impressive. I was a
little skeptical until I saw the stuff. Oh *man*. The EHing will help the turbo spool quicker.
The Swain coating not only helps the turbo spool more quickly by keeping the heat in the manifold, but it also keeps under hood temps way down. My car is no hottter under the hood than my car was NA with the header. I'm deadly serious. Good stuff.
http://www.swaintech.com
If you use either service,
please do me a favor and tell them you read about it in SCC in the G20 DET swap article.