190 on .25s sounds way too low,and you have a tightbore which means that's even worse,tightbores generally increase velocity by a fair bit. Sound like air seal issues. It could be that the tight bore installed was fudged and the hop up rubber is not installed correctly. I'd crack open the hop up to try see if the hop up rubber is in good shape. Airsofters also love to wash things with silicone magic oil,I'd give the rubber a good rinse in some warm water just to get any crap off of it. Wash it in fiary liquid if there is a noticeable deposit of crap on it.
Once installing it again wrap the end of the rubber with PTFE tape or better yet,dental floss.
If that does not sort out the FPS issues it could be a sleuth of gearbox issues.
Once you have the accuracy and air seal issues done ( the most important ones) Then you can move onto gearbox work.
If you want high trigger response/high RPS Here's what I'd recommend-
Chinese high torque neodymium motor (preferably 20 TPA or more,ZCI,Chaoli and JG make good ones) SHS motors,although at only 16 TPA are also very good and efficient.
Low resistance wiring
Basic Mosfet- Gate Pico SSR2s are very popular. I however often use ASG 'ultimate' mosfets since they are very easy to come by for me and rather cheap. I ran mine on a 35c 9.9 LiFE with no issues.
High speed gears - SHS 13:1 gears and SHS 12:1 gears are good quality. They've improved their machining quality on the latest batches now and no longer have bevel gears that like to grenade themselves.
Good shimming- Bad shimming often creates stress & resistance on the gears which you do not want. Make sure Bevel to pinion contact is perfect. May be hard since some V2 guns which house motors in the pistol grips have poor alignment - G&G is an offender on some models on this. Tokyo Marui and ZCI pistol grips give the best motor alignment I've found.
AOE correction- This is adding spacers on the cylinder head (Usually sorbothane) to make sure the gear contacts it at 90 degrees to prevent wear. On guns with higher RPS on stronger springs or guns which use higher power batteries like 11.1 lipos this is a 100% required job- My opinion is that manufacturers should be doing this out of the box but whatever. It preserves your piston to a great degree. Also by using sorbo pads to space it out you reduce stress on the gearbox shell. Two birds with one stone.
A good website for this sort of stuff is Airsofting Tutorials. Offer well presented advice on how to mod the guns.
http://airsofttutorials.com/
When looking for shimming guides search 'bevel to pinion shimming' This is the most efficient way to shim gears as the bevel to pinion contact is the source of 90% of the screech in a gun.
Use the google for terms which you might not understand.
Or you can buy the right parts and send it to a reputable tech if you are not comfortable doing it yourself just yet.
