ses light flashing and misfiring badly

Hey , one word of advice for ya !!!! when ses light is flashing that means that you are doing damage to your catalytic converters....i would drive the car as little as possible until whatever problem is fixed.....Ford should have told you this right off the bat...It obviously sounds like you have bad misfiring going on there and i cant believe they are having such a hard time figuring out the problem....anyway, just thought id share the info with you....

By the way...I have an 02 gt also with 37000 on it and no problems so far(except the usual petty bs..)

I am willing to bet it is your crank pulley bolt backing out since you said you have pulleys. When the bolt backs out, the crank pulley wobbles and messes up the timing sensor. Mine did this and I had the exact same problems: SES light, began flashing at highway speeds and engine misfired. The bolt that Steeda tells you to reuse is actually a torque-to-yield bolt. It really isn't intended to be reused. The steeda instructions compensate for this by basically instructing you to torque the hell out of it. Try to re-torque it and see if that helps.

FUNXGT:

Along the lines of what "bennyjammin" said: check the crank position sensor. If the pulley is snugged up properly, then it could be the sensor.

Good luck and please post back with what you find out.