Have 500 miles on fresh topend. Just started stuttering last week for some reason. Between 5k-6k RPM it will stumble a little and shift light will blink the same as the stutter. Rev limit in MSD is set at 6500. Any ideas???

 

Does it happen or get worse as the car warms up. Mine cold would rev perfect no studder backfire or miss. As it got warmer it would pop once at WOT a split second before shifting. Hot it would pop violently 5 or 6 times out the exhaust like it was on the Rev limiter or hanging a exhaust valve.

Changed plugs
Wires
Checked for codes none
Tapped into the schrader valve on the fuel rail with a mechanical gauge. pressure was good.
Lashed valves
Changed fuel filter
Coil ended up fixing it. I guess it was breaking down as the heat under the hood increased.

Are you A4 or M6

 

like said above. Check all those things. If everything checks out fine. It could possibly be your opti. My car had a slight stutter just like yours. It would only do it when i would rev out a gear at 5-6k rpm. How old and what brand opti are you running?