When I floor my 03 XS to pass, it kicks down but bucks and surges badly until I get off the throttle.  Is there a kickdown cable or adjustment, or could this be an engine issue?  It has 105K miles; plugs/wires/fuel filter were done 2K miles ago.

Auto? Manual? Sounds like torque bind in the center diff/MPT. In autos it's usually caused by a failing Duty C solenoid.

Torque bind usually only happens when turning.

 

What brand and type of plugs were used and what brand of wires? Those 2.5 engines are very picky about plugs and wires.

Air filter been replaced recently?

Automatic. NGK plugs, OEM wireset, 4K on air filter.  This only started within the last two weeks or so.  The ATF was changed multiple times after purchase (101K mi.).  Tires match and no torque bind in tight turns.

Dirty MAF might do that.  That's an easy one to start with.

 

Is it only when you downshift?  If you floor it from a standstill will it buck around when it gets to higher RPM?

Why kind of NGK plugs?

 

Make sure the wires are clicked on all the way.

I`d check the fuel pressure while driving despite the recent pump and filter.

Fuel tank screen could be a problem.Did you replace it?

Most pumps have no warranty if you did not.