Wes is right - revving in neutral means nothing. My money is on the fuel filters, or possibly the fuel tank strainer (not fun to remove & clean that though). Note - when you replace the spin-on canister filter, fill it up with clean fuel or Diesel Purge, or use the primer hand pump to bleed the system. Otherwise you'll probably kill the battery trying to start the car with an empty filter...! BT, DT.
Would not hurt to check the brakes also, the old rubber hoses can constrict and cause dragging - common problem, cheap fix ($9 per hose x 4). The fluid needs changing every 2 years anyway, so plan on doing that as maintenance soon.
Also, about the power: that car should get 0-60 in less than 14 seconds (timed with a stopwatch). If it's 20+ seconds, the tubeo boost pressure line from the back of the intake manifold to the ALDA (square thingy on top of the injection pump) is probably blocked, or the switchover valve is plugged. Fix that and you'll be shocked at the power increase!
Good luck,