Hi, I have a 2000 Subaru Outback. I had it repaired about a month ago because it had been accelerating very poorly, hesitating, and misfiring. Then one day it just stopped and would not start again. The mechanic I had it towed to put in new spark plugs, timing belt, and water pump. He also put sealant in the radiator and did an oil change. The check engine light had been on. The mechanic who fixed it said that the CEL had to do with the spark plugs. Got it home and it is working great, but then the CEL came on again (before I even got it home). I had it checked at same mechanic and at AutoZone. Codes p0325 (knock sensor 1 circuit malfunction) and p0420 (catalyst efficiency below normal) came up. My inspection is due in April. The guy at Autozone sold me a fuel system additive and told me to use premium gas for a week and then come back. The mechanic told me it will probably need a new catalytic converter, but might not need a new knock sensor. I’ve been trying to research it online, but I’m not really a “car person”. A friend said he thought there are tricks to get it to pass inspection involving fuel additives and driving like 100 miles. He even gave me written instructions. Are you familiar with this? I don’t know what to do. I’m living on half my usual income paying back loans from clients and friends for the previous repairs, and for the new front brakes I had done in the fall (pads, rotors, and driver’s side caliper). Can you give me any insight or ideas on what to do? Please let me know.