Airsoft Canada - maybe its just me....ICS A3 issues

after about 8 months of play my prized ics -a3 was shooting a unacceptable 286fps,,,down from 340fps. after being adament about playing with an out of the box stock weapon until the spring sagged ( well,,i put metal bushings in but thats it) i decided i had earned the right to upgrade. what a mess,,,was an easy enough swap being a split mechbox but one simple spring upgrade sure upset the balance of the rifle. went to a systema m120. nice quality part,, installation was a snap,,,but only having an 8.4v 2400 m/h nicad the rate of fire seemed as effective as trying to run underwater. forget semi auto,,cycling was erratic and undependable. the weapon shot a respectable and consistant 377fps,,but no more double tap kills with an erratic semi auto,,,,and no kill is more satisfying when you run someone out of ammo in their high-cap pop up and give 'em two in the chest ,,,, so i took the m120 out and put an m100 in( was a gimme ) and im awaiting a piston/piston head to go with the new spring. im hoping i will get a better air seal with this combination. i also plan to go to a m110 spring in the near future. with a better air seal an m110 i should be around 380-390. to make this long story short,,upgrades need to be chosen wisely,,if you are not going with high torque gears/ motor /battery to accompany a high spring upgrade,,,,dont bother. it will only upset the balance between reliability and dependability.