mk3 power plenum...now a valve leak?

I have the wc mk3 compact 22 and I love it. Problem is, I can't seem to leave well enough alone and decided to add a 1.2" plenum and Huma reg pressure guage.

I took my time and tried to be as meticulous as possible during the installation. I degassed the rifle slowly via the reg pressure guage. 

After reassembly, it wouldn't hold air. It's leaking through the barrel, which I assume, indicates a leaking valve? I took it back apart to check for signs of dirt, damaged orings, etc. Nothing obvious. I did not remove the valve seat. I tried but was not having any success.

Can degassing the rifle via the reg pressure guage cause damage to the valve? Is there an easier way to remove the valve seat for inspection?

Anyone else have this happen?

JP
 
If cocking doesn't stop that leak and assuming you don't have a tank to fill it and you aren't able to pump it at rate of 100 miles per hour you can put it on safe and double load 2 felt cleaning pellets or 2 pellets to block that air so you can get a seal from zero start pressure. Be sure to point it in a safe direction and put the gun on safe. Be sure your shroud and LDC are removed when you fire those 2 cleaning or lead pellets or else you may destroy your shroud endcap and LDC due to clipping.