1994 BMW 318 Loss of power, bad acceleration, bucks when sh

I have been dealing with a weird issue for quite some time now with my 1994 318i. It is an intermittent problem, and doesn't happen too often, but it happens often enough to cause concern. During this time, when I try to accelerate it sputters and takes much more effort to gain speed, and I hit each gear during this time, the car bucks forward. Then when decelerating it will do the same, and when it almost comes to a stop it will feel like it wants to die and sputters until idle, upon which everything is fine at idle. Since I've had the car I've been suspect of the fuel pressure, as the car still would accelerate poorly, but I first noticed this issue upon installing a K&N air filter, and don't know if this may be the cause of the problem, or if something was disconnected. I've had spark plugs, fuel filter, air filter, tranny fluid replaced. Some have said that all this points to a bad fuel pump, any thoughts? I have no "check engine" light on, nor have I ever seen it light up while driving. PLEASE HELP ME!