On my 2000XK8 when cruising at abt 35 or 40 then pushing up to abt 80 at almost full throttle runs great. When cumming back to 30 or 40 to continue cruising feels like it's getting too much fuel. Clears up in abt 10 seconds. Feels like fuel problem not not plugs or coils. Any ideas what this could be?

 

Have you checked for OBDII codes?

 

Have you cleaned your Mass Air Flow Sensor? Easy to do with a spray can of MAF sensor cleaner (remove two screws and the sensor is in your hand) and it often corrects mild engine stumbles (at least it does on my wife's XK8). As long as I clean it about every six months, I get no engine performance complaints from her....

 

Yes, cleaned mafs and put in a K&N filter abt 4 mos ago. Could be the
K&N had too much oil. I will clean mafs again. Tnx much.

 

No, but I will.

 

That K&N air filter could be your culprit. I know K&N fanatics love 'em, and I do not doubt their effectiveness in proper applications, but I'm just not willing to take the risk. Oil in the airstream causes too many known problems....

 

Would be a good idea to know what your short and long term fuel trims are showing when it happens. Could be throttle body problems.

Something like the Torque app, with bluetooth obd adaptor and android smart phone. Torque OBD2 Wiki

I use an Ultragauge which is excellent, but I am not sure about use with the 2000 model.Though one worked well with my 1995 XJS, just not so many gauges available. UltraGauge OBDII Scan tool & Information Center