I had a similar issue in mine with a modified fuel bucket. Feels like the car lost all power? Picks right back up when the car straightens out? That's exactly what I had felt. Instead of pulling fuel from the reservoir, my fuel pump was pulling directly from the tank, and going dry in a hard left with less than 3/4 of a tank (per the gauge which is certainly not the most accurate). Not sure why you're not seeing it in only first and not other gears, but that also may be for really hard accelerations when turning I'd guess.
I'd take your pump out, make sure you are pulling from the reservoir bucket, and not directly from the tank. If you don't have it modified, make sure it isn't cracked and is holding fuel. Trying to reproduce this too much will certainly lead to damage to the engine. If you don't drive hard in those turns, then you should be fine for the short term!