Hello guys!
My car had that issue since I was in Germany but never had the time to fix it. I was trying to figure out why my coolant lever sensor light was on even with the sensor replaced and BINGO! Found an issue with the HKS Twin Power harness. On this video, I talk about some of the reason of why your car might hesitate or back fire at wide open throttle (WOT) and how to fix it! I know this probably has been cover several times but it might help you if you are running with the same issue and can't figure it out! Enjoy!