hey everyone, i got a 87 gt 5.0 with a 5 speed and since ive gotten it ive advanced the timing to 12°, did a tuneup and changed the fuel filter. now i have absolutely no power under 2500rpms. it was good b/f all this, now it falls on its face until 2500rpms. i though i might have retarded the timing instead of advancing so i rechecked it. it acts like the timing isnt advancing. any input would be appreciated.