My car is a 99 GTP and I recently purchased a fuel pump (ZZP350) and I've had it installed since I got it about a month ago. It works great but a few days ago I ran into a problem. I used the big o-ring that the pump came with that seals the canister assembly to the tank itself and now it is not sealing properly. I had no problems for the month or so since I installed it but now when I top off the tank fuel pours out of the gap between the canister assembly and the tank. I did not remove the canister or mess with anything at all, it just decided it didn't want to seal anymore. I checked and the snap ring that holds the canister assembly in place is installed correctly. I had a friend drive around while I was in the back seat looking through the trap door, and I could see fuel coming out when we went around corners and such. It is definitely coming out as a result of the canister assembly not sealing to the tank. Is there something I did wrong? Was the big o-ring that came with the kit supposed to be used there? Anyone seen this before? I've never heard of it happening so I'm at a loss and any help would be greatly appreciated.