Every big shop that knows about running an evo at the track always tell you to NEVER drag race the car on less than a quarter a tank on the stock tank. This has been a known fact for a long time. The horse shoe shaped tank are on of the most inconsistent fuel supplying tanks ever made, even when a sump is installed. This is common knowledge. Hence why most people who use the stock tank feed fuel to a smaller surge tank. Then the feed out of that to the fuel rail.

On top of that, considering that gas is about 8 lb per gallon. The difference between an 1/8 and a 1/4 is only about 1.75 gallon. This is assuming that the X has a 14 gallon tank like the IX. So in short, your engine got starved for fuel over less than 16 lbs. Not worth the weight reduction in my opinion. Just because you have a bosch or aeromotive fuel pump does not mean that it can supply fuel under all condition. Plus if anyone has looked a fuel pump housing made by mitsu, you will notice that the sump line from the passenger side of the tank is only about 3/16 inch inside diameter. So the flow from one side of the tank to the side of the fuel pump will never match the fuel pump itself. Reason being the fact that the main fuel line to the rail is 5/16. You would be amazed how much the volume of fuel can change when just 1/16 is added in size.