Define "Stall" -

• "Engine quits running and I wander off to the side of the road and get it restarted.

Or.................

• "Engine hesitates, loses power, runs rough, etc., but if I back off the throttle, it keeps running".

That seal is important, but the car will run with the airbox completely off the car. It sounds like the seal you got is the wrong part, but I still don't think that is the issue here.
I'm questioning fuel pressure and flow. Also, mine did odd stuff during hard, HARD acceleration - 12 plugs and 12 plugs wires, at 101,000 miles, cleared that up.