We could really use more information in order to eliminate the possibilities. lets start out with the following:
How many miles are on the car?
Does it happen every time you start or just when cold or hot?
how many times does it happen when it does? One time, two times, multiple times or every time you leave a start?
what else have you done other than fixing oil leaks? When is the last time the spark plugs were changed? How about the distributor cap and wires? when were the valves adjusted last?
what is the weather like when it happens? Dry, humid or wet?
how long are you using the car for before it happens?
what is the engine temperature? cold, normal or hot?
what is the engine rpm when it happens? does the rpm drop when it bogs or does it hold steady as you press the accelerator down then catch up?
does it always happen at the same spot? if so, what is the road like? incline, flat, decline?
too many variables to make an intelligent guess.
if it only happens the first time and the engine is cold, look to the engine temperature sensor.
if you haven't had the valves adjusted lately, then you do the normal maintenance, replace the plugs, the wires, the distributor cap and rotor and have the timing set before you go any further as it could be simply caused by a worn cap, rotor, or plugs.
hope that helps