'81 733i hesitates badly

Recently bought an '81 733i w/ 80kmi. great shape, runs good at idle (700rpm) runs good down the road, but when I step on the accelerator to start (soft or hard), it hesitates for a split second to maybe 2 seconds. pretty frustrating. Changed plugs, cap, rotor, wires, and fuel filter. Still hesitates. Haven't bought service manuals yet but will soon.

Any help?

Check your fuel pressure. There are two pumps: a low pressure transfer pump located in the tank, and the high pressure pump located back by the fuel filter. If either of those fails (and the low pressure pumps have a high probability of failure) you will get hesitation. Also, if the low pressure pump fails, you need to fix it soon cause it invariably leads to failure of the high pressure pump.