ProTanks can take some fiddling.
I was getting really muted and sometimes metallic flavor, til I tried the following - now I bought more.
A) If you get the "metal" flavor, WASH IT WITH SOAP. I tried water, boiling water, and vodka - no help. But soap (not the coil - just the rest of it) got rid of that problem. Must be some kind of coating that they come with...
B) Remove half the flavor wick. I found this lets more juice get to the coil, and improved the flavor. And it didn't cause any leaking. You need SOME, but there's too much in there. There's youtube videos on how to do it, if you haven't before opened up the coil head of a ProTank...basically you pop the airtube off.
C) Finally - not sure why, but the ProTank MINI doesn't need any of that! I like the ProTank shape and size for a big tube, but on an Ego device, I don't think anything beats a ProTank Mini - no leaks, great flavor and vapor, right out of the box.