Recently had my suspension sorted at RC Developments.
The car was fine afterwards but they suggested that they could hear either a little piston slap or maybe the crankshaft making a little noise so keep an ear open.
As I understood you only got piston slap on a cold engine (and I doubt that was the case) then it must be the crankshaft. So the obvious question being that it won't get better on its own is how big will the bill be to get it sorted ? And what are the options once it opened up so to speak ?
The car is a 95 WRX which is mechanically standard

 

Chris, not necessarily, piston slap if allowed to deteriorate will eventually be present all the time. If it is slap then it can be annoying but rarely life threatening to an engine.

If it is the crank then it needs to be fixed quickly before major damage occurs. You need to visit an engine specialist who will give you an ear and an opinion and then start looking for a rebuilder.

We can help, but l guess as you went to RCD, that you may be some distance away from us. If you like, give me a call and l'll talk you through the options without any obligation to spend money.

David API Engines