I HAVE A 6 SPEED Z28. I'VE NOTICED THAT WHEN IM TAKING OFF FROM A STOP IF I ACCELERATE ABOUT HALF THROTTLE I DONT HAVE ANY PROBLEMS, BUT IF I PUSH IT TO THE FLOOR AFTER I LET THE CLUTCH OUT MY CAR STUMBLES AND THEN WILL ACELLERATE. I HAVE TRIED TAKING OFF FROM AS HIGH AS 3K RPM. IT HAS A NEW CLUTCH, SO THATS NOT IT, AND I DONT THINK ITS THE OPTI-SPARK BECAUSE THERE ISNT ANY OTHER PROBLEMS.