Misfire on 3.0
 

I have already repaced both vavle cover gaskets, 6 new spark.. plugs, and 6 new ignition coils.....and still have a misfire when I try speed up anyone have other ideas?

Year, mileage please. Any known codes---please list all. How long did you drive with misfires?
Did you change all 6 intake plenum seals: OES Genuine W0133-1639826 Intake Plenum Gasket | Auto Parts Warehouse See also My Pic: Green Rubber Seals.

Did you change the throttle body gasket/seal: Mahle W0133-1807640 Throttle Body Gasket | Auto Parts Warehouse .

The above should have been changed as intake plenum removal is required to change plugs/ign coils.

https://www.mazdaforum.com/forum/mem...off-2-2223.jpg

Missfires can be caused by a million and one things:
Vac leaks
wiring issues
spark plugs(even fresh spark plugs that are crappy quality.... E3 and such)
Ignition coils
alternators(search EMI)
MAFS
injectors
injector o-rings
intake gaskets
TB gaskets
PCV hoses
PCVs
malfunctioning EGRs
Malfunctioning CAS
o2 sensors
aftermarket intakes
intake hoses
vac lines
Timing chains
timing chain tensioner
Broken cam gears
Malfunctioning cam sensors
Incorrect Crank gears(the I4 has like 40 different configurations for whatever reason)
incorrect PCM flash
issues within the PCM
PCM wiring
bad diaphram within the FPR
issues within the fuel pump
dirty fuel filter
dirty fuel lines
Pre-Cats

If the above gaskets/seals have not been changed, change them. Clean your MAF sensor, throttle body.
Change your PCV valve and probably that short hose as well.
Inspect the intake accordian tube for cracks. Inspect for vaccuum leaks.
Put in a good Fuel system cleaner: http://www.redlineoil.com/product.aspx?pid=80&pcid=12
Inspect wires. Re-set ECU after doing above.
On the 3.0 ltr V6 the above are easy to do as MAF intake accordian & throttle are removed when removing plenum. PCV is also easier to get to when intake plenum is removed. Clean EGR as well.
http://www.youtube.com/watch?v=dmZOn...eo1k3lezmJdHyW

After this comes more expensive stuff, so do the above first.