Need Help, Fuel Tank Venting!!!

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I didnt know i had an issue until i took the car for a track day. I was spilling fuel out of the filler cap with hard left turns. I noticed the filler cap had the rubber gasket removed. I installed one/ borrowed from another e36 at the track. It stopped the fuel dumpping out on the track, but would cause my car to stall out and create pressure in my tank (opening the cap you could hear a huge air blowing noise. So its choking the engine out i'm sure restricting the near 0 pressure return line. As i bought the car with the swap already done i am not sure how much of the fuel setup would be from the 318 and how much from the 95 M3. I do know that the filter is in the stock ti place. Suggestions for what i could check would be great!
Thanks