Need help... Can't drive off... Engine just keep stalling...
 

My son's 90' Miata has developed a weird issue that's proven to be quite difficult to figure out. Up until about 3 weeks ago, the car was driving just fine until one day it wouldn't start because he left the lights on overnight. Gave it a jump and it started fine. He drove it to school and was fine. That's until he tried getting home. The car would start without problem. But as soon as he engages 1st gear and starts to get going, the engine would stall. Giving it more gas than usual doesn't keep it from stalling, Since the battery did die the night before, I'd replace it with a brand new one just to be sure. No difference. Nothing works... give it more gas... slower on clutch release... it would just stall.
We ended up towing it to a shop. We've used this guy on different occasions to work on the car with good results. He came highly recommended from a Miata forum. But for the life of him, he can't figured out why this is happening. He did try to give it a lot of gas... like when you're about to do a burn-out... and then let go the clutch very very slowly... The car does go... for about 15 feet or so... before it stalls again.
Any suggestions?