Tuning Impact mk2 tune not returning.....

so before I started trying to get my slugs working, I took all the current measurements off my impact. noted everything. got frustrated as no matter what I tried with my cast slugs I cant seem to find the magic spot for them as of yet. I can find a decent spot in the mid 700 fps range but not where I want to be. I'm not after power, I'm after accuracy with power secondary.

So when I went to reset to my good pellet tune that I was using previously, its coming in way too slow. 
Are the regulator gauges that bad on these? I'll say the impact is only 4 months old and has the black face gauges. the bottle pressure gauge lines up good with a full fill of my compressor's gauge. If I do get another gauge I may opt to go digital. Sekhmet probably. pretty sure the Impact gauge thread is 1/8" bspp.

Where/what else could I look at that would cause an all most 200 fps drop?
 
No . Long time now they don't have a set screw in c1.just put a very small drop of blue loctite and any time you need to open it again just heat it few seconds with a pocket lighter.

Just a tip.if you can't install it again and you think that something is going wrong with the threads( very tight while you installing it in valve rod) you can burn again the inside of the c1 with a pocket lighter and drop a little brake cleaner inside.It dissapears all the old glue.Just wait to get dry before you install it with new loctite.

Same time clean carefully the threads of the valve rod and everything will work like a new. 

This is my way and trust me I made it more than 50 times last 6 months.( is the stupidity😂 and the pation and the curiosity for different tunings with different internal parts !!!.Nothing wrong with the gun .