It's exactly what you said.. Cobb doesn't recommend using catless dp used with AP because of the risk of over boosting with the stage 2 maps. I hadn't been planning on going catless. I was planning on replacing my rotted dp with a used oem, but I got the invidia for $100 so if I plan to go catted instead, it'll be easy to recoup my money. I don't have any experience with tuning so I'd rather err on the side of caution and listen to the people who at least seem like they know what they're doing. I did talk to a couple guys on here who didn't have issues with the AP/catless so maybe the possibility of over boosting is slim?
Straight from the horses mouth:
"A catted downpipe would be best. We always recommend using a downpipe with a high flow catalytic converter, not only to help meet emissions standards, but also for performance and safety of the car. In some vehicles we support, using a race or non-catted downpipe can cause boost creep, or uncontrollable boost. This is typically something that tuning can not fix as it is a mechanical issue that can only be resolved with a catted downpipe, porting the wastegate, or by using an EWG with a custom tune. You should keep a close eye on your boost levels to make sure the car hits the proper boost target and tapers towards redline.
Kyle@COBB"