I have a 90 gtst that has the common misfire problem. It happens at 40-100% throttle around 4000-5500 rpm. I can take the car all the way to redline at 25% no issues. The car holds boost all the way even when the car is misfiring/sputtering. The car idles fine and runs fine otherwise., and occasional i can do a full pull 100% throttle, however it is random. I have tried three different spark plug gaps and two types of plugs and i have replaced the coil packs and the issue still remains. The car idles fine and it is running on all 6 cylinders, so i do not think it is the igniter. I am now stumped because i thought this was a spark issue and now i am thinking fuel or maybe a bad maf?