I've taken the liberty of moving your post to the Spider section. It will likely get more replies there.
First - is this a USA Spider? USA Spiders have L-jetronic fuel injection. See the link in my signature to a page of info about the L-jet system in our cars. Note that the 'L' refers to 'Luft' (German for air). L-jet depends on accurate measurement of all air entering the engine to calculate how much fuel to supply. Intake air or vacuum leaks mess up this calculation leading to running problems. So make sure all hoses and air ducts are in good condition and tightly attached.
Vacuum leaks injector connectors replaced with pieces of rubber hose pieces (yes it works for a while), bad manifold hose nipples, bad cold.start valve.
Bad pressure booster and hoses, etc.
Buy a can of starter fluid in aerosole can. Gently and cautiously spray the fluid arround the intake across over hoses and their fittings on top of the engine, while the engine is ideling. if you have any unregulated air leaks in the intake system, they will show up when you spray the fluid as an increase in idle speed. With a 1988, you can expect to find some, particularly in the accordion bellows on the cross over pipe (hard black rubber). Fix these unregulated air leaks and your sluggish acceleration problems should disappear.
Thanks for the help. I tightened clamps around bellows, one was very loose. Car accelerates perfect. Both fuel pumps were replaced before I purchased car, however; I'm still not completely confident that they are working properly. I had looked through some post and noticed that the pumps seem to make a noise. The noise on my car comes and goes, fuel level doesn't seem to matter.