The 1/4 tank stalling is common in 92-93. The baffles in the fuel tank are known to break free, allow sloshing and basically fuel pump starvation around corners, at stops and when aiming down hill.
Airflow.. this is a tricky one for your car. Does the airflow move on it'* own. Say you pick AC..will it move to the dash vents? 92-94 electronic climate control had it'* programming and it sticks to it. There was no option in these years to choose where the air went. Heat automatically is directed to the floor, defrost to the windshield and Ac to the vents. It is possible to change this by swapping the headunit and HVAC programmer. If the air is coming out floor and dash both ...as well as only. Check the vacuum can mounted to the firewall, right next to the wiper motor. Most likely your hesitation and the HVAC are related to a vacuum leak.
00 Regal GS: All kinds of cool stuff.