My 97 xjr has recently developed a loss of power issue at wot. The car runs and drives beautiful any where from 1/2-3/4 throttle, but in sport mode full throttle the car seems to have a no power "sorta like a bad clutch slipping" on a manual transmission car, the revs go up and just hang there, but it doesn't want to move. I was thinking maybe it has a fuel related issue like a dirty filter? I just recently finished doing the water pump and it started occurring after. I was thinking about testing the coil plugs and changing out the spark plugs as well. No check engine light(s). Any suggestions?

 

I found my problem, thanks everyone. The gasket flooded my spark plug and coil plug:

 

It would seem a miracle that it ever generated any power at all in those circumstances. I hadn't realised just how dramatic that oil issue can be!

 

I was also getting a cylinder #6 injector code every now and then, but I took the cover off and found the power wire crimped. I tested cylinder #1 with a dvom and got 12 volts and cylinder #6 was getting about 6-7 volts. I repaired that also, but hopefully this can help someone out in the future if they have a similar issue.