Over the weekend I was running WOT and the engine would quit. I pulled the gas tank from under the deck and, even though the air valve was open, I noticed that the tank looked like it was dented(like air was sucked out of it). I thought maybe because of the 100 deg weather were having. I remove the fill cap and put it back on and it ran great after that.

I recognize it was probably vapor lock, but my question is are there better gas tank options out there. I have very little room under the deck and it is a really tight fit. Do they make lower profile, 6 gal tanks?

Are you sure the air valve isn't plugged? That shouldn't happen if it's open fully no matter the temp. You could get a new cap with a vent and try it instead of a new tank.

funny thing is I just put a new cap on because the air vent on the old one broke off and is under the floor. It broke off when I shoved it under the deck.

Try the Moeller Marine tanks- they have lots of different shapes and sizes of tanks to fit a variety of applications. Or get on summitracing.com and look at the aluminum fuel cells. I had twin 6 gallon tanks that I replaced with a single 15 gallon Moeller Marine FT1598 tank, it takes up less room because I cut a small compartment under the front bench seat for it to fit into. Got it for $30 on craigslist

So this started with a new cap?