Good call on testing it first! I am in the same boat as you - installed a Mishimoto last Spring, found out there was a very small pinhole leak (mine's located on the top bung weld, right of the filler cap). Mishimoto covered it and sent me a new radiator - but I had to wait a few months due to backorder and supply issues. Because I had to wait I ended up just taking a metal punch and hitting it in the pinhole - still weeps but barely; it's been like 6months and thousands of miles, so I feel alright about it as-is. I haven't swapped the radiator due to laziness but if I do I'll be sure to pressure test the new one! I don't have a TIG welder, but have thought of finding someone with one and just have them put the tip on the pinhole to see if that does the trick to seal it up quickWarranty claim was filed with Mishimoto Friday, and I just got notice that the replacement radiator shipped today, Monday. I really don't want to spend the time reinstalling another flawed radiator, so I will likely try to leak/pressure test it before I make the swap.