Stalling on a turn is an indication that one of the accessories on the front of the engine is "freezing" up and causing the crankshaft to momentarily stop turning long enough for the engine to shut down. The reason this would occure on turns is that the engine is on a large load during a turn because of the power steering, similar to the load of an incline. So if thestalling issue, went away after the alternator was replaced, it's possible the alternator had a front bearing that was freezing up and causing the stall, and no charge condition. Now after replacing it the belt tensioner or sepentine belt might have loosend or gotten weak, so around a turn the belt may not be spinning the alternator, which would be difficult to catch on regular testing. There are tools out there to check belt tension on this type of engine, have this done and the belt removed and power steering pump pully checked for binding. Another item, GM had problems with their positive cables becomming slightly loose on the battery and this caused a voltage drop to nthe computer. Check both cables and the battery health. Even if they seem tight, if you pull on the cable end upward, it should not move. If the battery is weak or shorted it will cause a new alternator to fail without showing any other signs. If the battery is older than 1 year, you may opt for replacing it if it shows weak under testing. Battery tests should be carried out by equipment capable of testing for shorted, unstable batteries.

-Rip