Sounds like you are confusing a leak down test from an automotive 4 stroke engine standpoint.. Leak down testing a 2 stroke identifies leaks that will pull in extra air and cause a lean condition. Doing a leakdown test on your engine will PROVE if/where air is leaking and actually identify or rule out the root cause of your issue. You could have a huge air leak and still have solid compression numbers yet still be affected by running issues from the air leak.
you mentioned cheap top end, what exactly does that entail? is it an ebay kit? a used set of cylinders/ pistons bought off facebook? you should expand on that so we can help you out.
As stated multiple times throughout the thread, definitely start with a leak down test so you can figure out which direction to go next. Much easier to spend $25 now and confirm that you do or dont have a leak before tearing it all apart and guessing, and then having the same issue and posting back here asking what to do next. help us help you.