[200q20v] speedo and boost,....Foggy windows.

[C1J1Miller at aol.com]

Does the TAP chipset include a 2.5 bar pressure transducer? From their web site, it appears as an extra cost option (and IMO should not be!!!).  Does the chipset also include a stiffer wastegate spring?

After checking codes, I'd build a wastegate frequency valve test light circuit, so you can see what the ECU is trying to do to control boost.  Sounds like your spring is stiffer than stock, and the ECU is shutting down the WGFV... thus limiting boost to the (stiffer than stock) spring tension setting.  Stock is 1.4 bar; that's somewhere around 6psi.  Can you reinstall the stock spring, and see if the surging goes away?

Where did you tap into the boost pressure line?  Usually it is done near the ECU; you could be seeing some occilation if the line to the wgfv was tapped into.
chris