the big one or small one?i plugged the small one.it just dont feel right.i checked its working properly,the flap is closing right.pac brake says big one,but the plug fits in small one.any one know for sure?also if i put a back pressure gauge on,what kind of gauge?and where to put it?big port or small,on the pacbrake housing?thanks

 

If you install 60lb valve springs you can block both holes.
I've done this on two trucks with Pacs, one has close to 100k towing a 14,000 trailer without problem.
Don't know if this is what Pac recommends, reason I did it is because my BD ebrake has no holes and works great. The butterflies are almost identical.
Might be wise to call Pac and see what they think, I've found them to be very helpful. They've even replaced five year old brake components for free several times.