Audi Repair: 1.8T low cylinder compression (#1), cylinder compression, valve train

Question
1998 A4
1.8T manual
132000 miles

right before I bought this awesome car the previous owner replaced everything as needed like the timing belt and water pump, but he also put on a used AEB cylinder head. He said his friend from a dealership did all the work so I assume it's pro quality. Once he put the new head on he noticed a slight valve train tapping noise and the compression in the first cylinder is 45. I know this isn't good and shouldn't be driven like this so I need to take care of it. He ordered a set of new lifters and he is willing to put them in to see if it cures the problem. If it doesn't fix the problem I might need to take off the head and inspect it and put on all new gaskets.

ever heard of anything like this before?


Answer
hello
If compresssion is low in one cylinder only , we know there is a problem. 45 is very low. What I do next is leak down , before I take anything a part. So I can find where the leak is. It may need just lifters ,but who knows
good luck              pltech