Having a hard time getting car to accerlarate and change gears

hmmm....it would seem as if your trans is having a bit of a hard time shifting so its sort of waiting before it can shift to the next gear (possible the gear system is having a problem shifting due to it sticking to some gears) i'd have to say....a mechanic can take a look to see why its seemingly shifting late at high RPMs to me IMO the trans is just having a hard time shifting with gears wanting to stick together making the whole trans have a hard time shifting

I suggest freezing the gear over night to shrink it a bit. And then applying some heat to the metal of the seat before inserting the cold Bendix gear.Be careful not to ignite any grease. Best done in an open well ventilated area. At your own risk.

If the shifter moves freely when engine is off. Its possible that the clutch is not fully dis-engaging causing stiff gear changes. May be time for a clutch

How are you having problems with shifting ?
Can you shift thru all 6 gears sitting still with the engine running ?

Sounds like the shifter may be wearing out. You may have to get into the transaxle to check it out. Could also be a problem with the alignment of the shift cable between the shifter and the trans.

when is the last time you had/checked your transmission fluid?
What about having fluid and filter done on it?

try having thbe fluid changed with the proper fluid. It may be low on fluid and this could keep the trans. from going into gear properly. Look at the old fluid when draing, see if there is metal in the fluid. If so you will need to have the trans. repaired.

time for a clutch

it needs a new clutch and preassure plate assuming it it a stick shift

you are having problems with ur clutch, need to bleed or adjust, if its easier to change gears after steping on clutch more than once, then all you need to do if bleed the system,