While driving last night in the cold weather (20 degrees) the Cayenne was surging @WOT on the freeway. Has anyone experienced this before? The boost gauge was going mid to full boost back and forth rapidly.

08' turbo with softronic tune, aftermarket diverters, bypass pipes, new plugs/coil packs a few months ago. I was thinking maf or boost leak? I had no CE lights on.

 

That sounds like what I was experiencing before I swaped out my valve body.

 

Haven't seen that before, but would unplug both MAFs and see if that still happens. Also, pull out your Durametric and check for codes in either the DME or TCU.

 

I had a surging issue on my 04 CS , it turned out to be the pre cat oxygen sensors that needed to be replaced. I changed ignitors (was changed by the dealer during a major service due to cracks) and MAF sensors without solving the problem before getting to the oxygen sensors. I had no fault codes, but experienced hesitation under hard acceleration and surging when coming off the throttle at higher speeds.

 

Surging is back. I think this only happens in cold weather! Still no codes. I had a similar feeling in a fd rx7 and it turned out to be clogged cats. Wondering if maybe my primarys are bad? Any way to test?

 

Since you're at WOT, a vacuum or boost leak would be more-pronounced and colder air is denser so perhaps it's leaning out?