If I slow down quickly when the tank is reading less than half the car will occasionally stall when I come to a stop, more often when there is less gas in the tank (no problems just driving along). Sometimes I can catch it and keep the revs up. Also I can't get more than 7.5 gallons in the tank (holds 11 gals) when empty and the gauge reads below full (~8/10ths) when I fill it up. I've looked under the car and can see no dents in the gas tank.

Your gauge might be wrong or depending who had it last check to see if they didn't switch the tank for another model or anything