1985 325e no power engine runs lacks power

that could be a timing belt skipped a tooth or two, or loss of spark to a few plugs, weak coil or loss of spark threw plug wires to engine block. and in some cases its starting out in limp mode and starting in a higher gear giving an effect its no power when in fact its no low gear

How long since your last major tune up? (Spark plugs, plug wires, air filter, fuel filter, ect)

Engine was used. Put used good plug wires on. Now can pull plug wires off few plugs no difference in running.