If you've got starting problems, it's less likely a matter of new plugs, and more likely that the CPS (if it has never been replaced) is deteriorating. Usually, the car has enough voltage to get through older plugs and wires, unless you observe a clear "miss" occurring in a cylinder.

In the older cars (pre '89, or so), the information about the crankshaft position is through the pickups in the distributor. After that, the distributor's role is relegated solely to directing spark energy to the proper plug -- no more advance/retard or the weights and springs inside of the older distributors.

The newer cars now have a Crankshaft Position Sensor (CPS) that is located as a sensor bolted on top of the bell housing, behind the engine (and, in our 240's, is a PITA to reach, sorry to say). The originals were prone to fail eventually, and the key hint that they're failing is that the car becomes hard to start.
The CPS should be replaced by a new version that will last the rest of your (if not the car's) life. I'm at work, so I don't have the info about the color (it's on my home PC), but you can tell the difference by their colors -- you can ask the dealer.

As for the difference in acceleration, I find the same to be true between both of my '93's and my old '84 -- the '84 is a bat-out-of-hell compared to the '93's. I think it's a matter of a lot of little design differences over the years, rather than just tune-up (I keep all my cars in fairly fresh plugs, wires, caps, etc.).