I have a weird question. Is it possible the springs in the clutch disk could be giving out? Recently I have noticed some drive line lag when shifting. I am not hammering it at all, just easy shifts. Seems to be some catch up going on after the clutch is let out and gas applied. Does not seem to be slipping, just a slight hesitation. No clatter or noise at all, engagement also is smooth. Throw-out bearing is quiet and smooth. Do ya think the disk could be faulty?  Drive shaft lash and u-joints have the normal movement but not excess. Acts the same with different drivers.

IS it adjusted with pedal play? so that the clutch fork has a little play when released?

Do you possibly have a rear main seal leaking a bit?

Do you have any drips of oil at the bottom of the bell housing?

A little bit of oil on the disk/pressure plate will cause it to get gummed up a bit.

You can remove the inspection plate and have a look.

Next... rear end fluid, clean and full?

Limited slip differential Supplement added?

Hope this helps

John

  Ya, a friend drove it to confirm the lag I was feeling.

  I doubt it is slippage, when punched, it gets out well. Its not a tire turner, but bites well. I am of the opinion it is disk deterioration. Once hooked to flywheel I do not believe it is slipping. Recent tune-up should not affect it.  I am going to pull the cover and look for pieces,oil,or disk dust.  Will let all know my findings.