Nissan Repair: 95 maxima very rough acceleration, nissan maxima, fuel injector

Question
I have a manual transmission nissan maxima. the rough acceleration occurs anytime there is load on the car (less if i accelerate very gently).
BUT the worst bucking/hesitation/violent shaking occurs consistently around 2500 rpm. the car won't accelerate at all for about 2 seconds (accompanied with intense bucking), then it will accelerate like normal after it "catches".  
i've done a tune-up (fuel filter, pcv, plugs, air filter), plus took to the dealer b/c of a check engine light- they replaced a bad fuel injector. the above problem is the residual of all the repairs. Thanks

Answer
Andy,

Check the distributor for oil on the optics especially since you complain of bucking at the 2500 rpm range.  The optical shutter wheel is beneath the distributor cover.  Take the cap, rotor, rotor post, and cover off the observe it.  If there is oil on the pickup or shutter wheel replace the distributor with a rebuilt unit.