V70 enignine missing at highway speeds

[allenjgoldstein]

I have a '99 V70 5 cylinder (non-turbo) with 127,000 miles, automatic transmission.
New spark plugs
New air filter
Belts look good
No other issues with vehicle.
Original engine and transmission with regular fluid changes
At highway speeds, above 65 mph, the car does not run smooth. While the tachometer and speedometer show no fluctuations, the car seems to buck or miss, giving the feeling that it is lurching ahead. If I drop the transmission down to 3, the same thing occurs.

I have had no other problems with this vehicle.

Any help would be appreciated.

[Jot]

You didn't mention fuel filter? at highway speed and an steady tach it must be fuel.