My gut reaction would line up with the preceding comments and your observation about your 993 - your clutch is dragging. A dragging clutch will typically show up as grinding shifting into reverse because of the absence of synchronizers in reverse. Have you had any incidence of grinding going into reverse? If no evidence of grinding, that suggests; but, is not absolute confirmation that the clutch is not the problem. The clutch may be dragging just enough that there is still torque being transferred through the original gear pair which makes it harder to disengage that gear pair. Also, my experience has been that a severely dragging clutch can complicate the shift into 1st and sometimes 2nd gear.
Your description I've learned to pull slightly, breathe off, and then it pulls out of gear smoothly. It only happens on some downshifts. smells a little bit like synchronizers. I am guessing that the pull slightly, breathe off, and then it pulls out of gear smoothly might be giving the synchronizer a little more time to accelerate the transmission input shaft (or the car is slowing down a little bit) to match up speeds on the new gear pair on the down shift. A big RPM match (rapid de acceleration) on a down shift makes the synchronizers jobs tougher because they have a lot of acceleration to do on the input shaft. If you are driving along at steady speed, say 100 kph and shift from 5th to 4th (or whatever depending on your transmission) and there is no balking in the down shift, that again suggests synchronizers. Down shifting gears at constant speed minimizes the speed matching that the synchros have to do. Also, does the balking only occur on certain down shifts or on all down shifts? If it occurs on certain down shifts that again would point at wear on specific synchronizers. If the down shift problem occurs on all gear changes, then I have no clue!!!
If you think it might be the synchronizers, the first thing to consider is confirm that the previous owner has the correct fluid in the gear box. A fluid change with Honda MTL can be useful, in particular because examining what comes out for wear particles might give you some clues as to whether you have a serious wear problem or normal wear. If fresh MTL does not help with the problem, then you can consider the synchromesh cocktails. A search on Prime will give you a range of anecdotal experience with the cocktails. There is some discussion about the effect of the friction modifiers on the LSD. Be aware that the friction modifiers that are applied to improve the operation of the synchronizers in transmission fluid actually reduce the slipperiness of the oil. This works because the synchronizer mechanisms are like little clutches which have to accelerate the gear pair to match speed. Reduced slipperiness results in improved 'clutch' action. The LSD also relies on clutch action and vendors of friction modified transmission fluid recommend against use in transaxles with LSDs because the modifiers alter the operation of the LSD. The reason this is significant is that the discussion of the 'cocktail' varies from 1/3 friction modified all the way up to 100 % friction modified oil. I would stay away from the 100% friction modified oil because the friction modifiers reduce the slip on the LSD clutches and will result in earlier engagement. There is at least one report on Prime of an owner who was experiencing constant lock up on his LSD in moderate cornering. The problem was resolved by draining his 100% friction modified oil and replacing it with normal Honda MTL.
The other thing to be aware of if you want to try the friction modified oil is that GM and other vendors sell friction modifiers for use with certain LSDs. However, these friction modifiers have just the opposite effect of the friction modified transmission fluids. Use these friction modifiers in your transmission and your synchro operation will go down the toilet. Make sure that you don't use this stuff.
As Larry B. says, that is my $0.02; however, in my case its probably more like $0.00002.
I had one in my hands last winter...
