The large hole in the output fitting should not cause any excessive pressure. If it is too big it will allow too much flow with not enough restriction (therefore no pressure) at low rpm. I know that one from personal experience
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I have blown the cap out of the back before also but never cracked the housing. How far did you go with the West Texas mod? I recommend only removing the factory shims and tightening the nut all of the way down. You can easily cause too much pressure if you start adding shims under the spring. That is how I blew the cap out on mine. If you want to mess around with the pressure I highly recommend putting a liquid filled gauge in the pressure line so you can see where you actually are at max pressure. I usually don't go over 2500 psi when you are at full lock.