My blazer is having trouble accelrating past 40 mph, the vehicle is running rough and slugish once it gets up to 55 the service engine light blinks i hav e changed out the mass air flow and did a fuel pressure check everything is normal just cant figure this out, its throwing out a multiple cylinder misfire,i checked my distributor its fine, any insight would help on this problem

Check the #3 O2 senser that is located just in front of the cat. really check the wiring that it connects to in that area, as mine had a wire pinched between the frame and the body ( from the factory) that eventaulaly wore through and casued the sensor to fail. usually no error code was set and the engine would stumble terrible from 40 to 60 mph. Had to replace the sensor with new, and clean out corrosion IN THE CONNECTER before everything was resolved.
there are 4 O2 sensors in the 97, 1 on each bank, 1 just before the cat and 1 after the cat. the one before the cat appears to be critical to set mixture, so check or replace that one first