[DeTomaso] Pressure cap question

[mike v]

Hi I was wondering what the pressure cap on the swirl tank should be as I have seen, read that is was between #13-16 caps but then I see on some of the Pantera site that sell parts and there saying #22 which is way too much in my opinion.
 I have a brand new motocraft cap that's #13 and when the motor gets warm it spurts out a small amount fluid, so either its bad or #13 isn't enough # for pressure

thx in advance for advise 
Mike #7042