Hi All, I'll try to keep this as brief as possible but I'm trying to decide on rebuilding my engine or fixing a blown exhaust valve in cylinder 1 of my engine. So basically a few weeks back I was driving home from a road trip and I started getting misfiring in the engine. Car was vibrating pretty badly and engine light was flashing. Brought the car to my mechanic and they found misfire codes on the ECU. Spark plug in cylinder four had the grounding rod half burnt away. Checked the cylinder with Boroscope and no pieces or damage visible. Upon further inspection all valves had significant carbon buildup so that was cleaned with walnut blasting. Also the ignition coils in cylinder 2 and 3 needed to be replaced. So that was done as well as all 4 spark plugs replaced. Replaced Intake manifold Gasket Elring and 4 seal kits. Did an oil change at the same time. Picked up the car and noticed a significant improvement in performance. I drove it for 2 Weeks and then the same problem happened again with misfiring. Brought it back to my mechanic and they discovered the Spark plug in cylinder 4 was again burnt up. It was then determined that the fuel injector for that cylinder was pretty plugged up and the other 3 weren't looking much better so had all four injectors replaced and again replaced the spark plug in cylinder 4. Picked up the car and again felt an improvement in performance even from previous repair. Drove the car for 2 more weeks and boom same problem again this time the vibrating of the engine was much more aggressive. Brought the car back to the mechanic and this time was discovered that cylinder 1 had very little compression. About 30 psi compared to around 180 in the other 3 cylinders. Did a leak down test and found that 1 of the exhaust valves in cylinder 1 has a hole in it. And this is where it stands currently. Haven't driven the car in a couple of weeks now. It was suggested to me that I have a few options. Number 1 is rebuild the engine completely for a cost of $13,500. Number 2 is replace the 2 exhaust valves in cylinder 1 and machine the head, as well as replace Timing chain, tensioners, and water pump for a cost of $5-6k, and Number 3 is sell the car as-is. Now I'm not interested in buying a new vehicle at the moment so I'm considering option 1 or 2. On one hand I feel like a full rebuild will give me a like new engine and many more years with the vehicle but is expensive and on the other hand I feel like replacing the valves and timing chain will be cheaper and fix the problem but something else could go on it a week later. So here I am asking for some advice/opinions on what this community thinks. I'm also really curious as to what the hell caused the hole in the exhaust valve in the first place. The car is a 2015 A4 Allroad with 195,000k on it. The rest of the vehicle is in good shape. Thanks for your input.