Have you done any upgrades (new striker spring. nozzle, etc.)? A heavier striker spring like the G&G or Polarstar springs would cause more gas usage, but I've never seen that use quite that much gas. It's also possible that if you replaced the air nozzle you either damaged it or it's seated wrong (actually fairly easy to do; I had a King Arms nozzle on my gun for all of a half hour before I damaged it while trying to make sure it was seated correctly).
Check your magazine, too: fill a sink with water, then gas up your mag. Dunk your mag in the water, and see where bubbles are coming out. You may need to disassemble it and apply silicone oil to the o-rings. Also make sure the
Also check the bolt - make sure the gas route packing in the hole that mates up with the gas route in the mag (the brass thing on the mag that goes up and down on top) is in place and isn't damaged. Try loosening the tension on the striker spring, but when you do this, make sure you loosen the grub screw at the back first (see photo; thanks go to Brainplay of ASF for the photo). Otherwise you'll strip the screw that goes through the middle of the spring.
I'm going to tell you now: The Tanaka-based M700 trigger system is a bitch and a half to get back in once you've taken it out. If you suspect your trigger to be a possible culprit, then I would first exhaust all other options.
EDIT: I did some reading, and it looks like the gas route bucking is your most likely candidate. G&G makes a set of replacement rubbers for the Tanaka; use just the gas route bucking and ditch the rest (the other two components are replacements for parts in the stock Tanaka hop up chamber). It'll cost you $10-15 + shipping.