it can be as simple as a timing step just off idle or a lean or rich spot, fairly simple to locate (in a vacant carpark) and it is generally a bit of trial and error to smooth out. It took about 20mins of start stops testing to smooth a sr20 i did awhile back to the point it was imperceptible.
Laptop and a tps vs timing log would get you on the right track to start, when it jerks look for a jump in timing in the log, if there is nothing there start playing with the ms values in the inj map. If that fails look at the accel pump values. I often see too much fuel in accel pump which can also load up the engine so it stumbles.