Not so much of a plan, as much of just wing it, there was a knock, but if you YouTube Impreza tensioners knocking it's very similar to what I was experiencing (I wasn't aware of this issue till after I'd stripped it so couldn't really "test" it As you say, correct timing and compression check, not got a locking tool, relying on good old paint pen(it's not failed me yet in 12years lol) Hopefully will be able to get the extra bits I need at the end of the month and get her back together , well finger crossed I will anyway! Loud pipes save lives