My car is a 2008 Audi A4 Quattro. I've had this recurring problem for longer than I care to remember. The code I keep pulling from it is PO299 which is "turbo underboost." The car has no "get up and go" to it, it takes a lot of time and effort for it to get up to speed and going up a hill is a pain in the neck!

Over a year ago, I took it to one place for this issue (I don't remember what they did) but it cost about $400. Car drove great for a week, then the light came back on, same code, and same lack of power.

About a month ago, I finally took it to another place and had a TON of work done on it - regular maintenance and trying to fix this issue. Replaced timing belt, water pump, pulleys, brake pads and rotors, and diverter valve (which should have fixed this). Car drove great for a week...then the same problem came back.

Took it back in and they replaced the solenoid valve. He said that THIS "should" fix the problem. If it didn't, then I'd need a new turbo. Again, car drove great for about a week..............and then the light came back yesterday and I have a lack of power again. I'm at my wits end!

My questions are:

1) Are there ANY other things that could possibly fix this without addressing a turbo yet?

2) If not, is the new turbo for sure going to fix this? (I don't want to pour another $2k into this if it "may" fix it.)

3) Why would it be fine for a week, and then like clockwork, get all screwy again?

4) Is it damaging anything in the car at all by driving it in this "condition"? I've been told by a mechanic in the past that its not hurting it...its just an annoyance.

Let me know what you guys think. I really love this car and want to keep it. I just want it to drive the way that its supposed to.

Thanks!