I recently purchased a TT which at the time was running great. Got an oil change only. Shortly afterwards i got the check engine notification. Autozone read a P1136 error which had me looking for an air leak. Found it in the brake booster cable. The cable had dry-rotted. I replaced this myself. I also discovered that the air filter tubing had not been connected properly. There fore the car had been sucking in air unfiltered. Now, I have notice that the car does not run as smooth as before. I sense some hesitation accelerating and the engine is loud. Any suggestions? I plan to have some new codes read soon.