Edit: parts are now about $60 on eBay, more info below.
Make sure to RESET/CLEAR YOUR CODES after install or it'll still show the code and be slow.

First gen (2007-2012) Acura RDX will sometimes pop P2263 and an SH-AWD error. There are different causes. Your dealer will tell you to install a new $7000+ turbocharger to fix it, because they don't sell the individual parts on the Mitsubishi made turbo that break down. You can often buy the parts and fix it yourself.

The most common cause is the VGT actuator wearing down. Some people call it the waste gate but that's not correct. It's made of a metal that is too soft. You can order the piece custom made from a machine shop for about $300 and replace it yourself, without removing anything from your car but the intercooler shroud. You'll need a couple 10mm wrenches, a couple screwdrivers, some wire (to prevent losing pieces), and some patience.

More info on this, and other P2263 causes and fixes, here:
https://acurazine.com/forums/1g-rdx-p...

Replacement parts:

My VGT Actuator was purchased from Southeastern Enterprises, [email protected] or 905-320-5191 (owner is Darren Gauryletz). He's a Canadian fabricator that makes the part from scratch from a slightly harder grade metal than OEM, so it shouldn't wear like the original. Mine was $300, prices are dropping though.

Others have had luck using Ebay for about $60. Search for "Acura RDX Turbo Variable Flow Actuator Eye Bolt." I'm not sure if the threading fits all RDXs. Make sure it's good metal (mine is 4140 and threading is m6x1.0 left hand). Too soft and it'll wear again; too hard maybe it'll damage/wear the linkage.
OEM part (will likely wear down): search for "49389-18470 U.S.A."