Help with my 98 custom

I just baught my 98C and it came with a 9 oz tank so i went to go fill it up i put the tank on the marker and when i pushed the trigger it shot once and made a farting noise and after pushing the trigger 3 times the co2 was gone then i went back to fill it up and it was shooting well about the first 100 shots and then did it again and now i bought a 20 oz tank and is filled but i dont know wheter to put it on cause it might do the same everything on my 98c is stock

Ya like Tallen said it doesn't sound like they are being filled properly.

They aren't filling your tanks properly then. Either the tech has no idea what they're doing, or they're deliberately trying to gyp you out of cash. Sounds like the tank isn't being properly pre-chilled and that they aren't scaling the tank the way they should. I suggest you confront them (in a professional manner) and explain to them that neither you, nor the individuals you have talked to, including a Factory Certified Tippmann Tech (that would be me), believe that they are filling your tanks properly.

Here are the steps to properly filling a CO2 tank.

1) Connect tank to an on/off fill adapter.
2) engage the on/off to open the tank's valve
3) vent the CO2 in the tank to chill the bottle and keep the new, incoming CO2 from expanding and blocking the influx of more liquid CO2 from entering. If the tank doesn't have any CO2 left in it, then some should be filled into the tank and vented off to chill the tank down.
4) with the tank empty and properly chilled, place the tank on a scale (an electronic fish scale from Wal-Mart will work well so long as it measures in half-ounces at the very least)
5) Tare/Zero the scale with the tank on it.
6) proceed to fill the CO2 tank until the scale reads 1/2oz below the tank's rated capacity (8.5oz for a 9oz tank, 19.5oz for a 20oz tank)
7) disengage the on/off fill adapter
8) vent remaining CO2 in the fill line
9) remove tank from fill adapter

It sounds like the either don't know to pre-chill the tank, or aren't using a scale to properly fill the tanks.

Dude, microwave corndogs aren't as bad as the cheese sticks that Jim makes. That idiot doesn't even us a plate half the time. I hate using the microwave after him.