You could have an intake seal leak as you mention but also check the wiring at the fuel injector, they had some problems with being strapped too tightly to the frame and as the engine shakes the copper inside the insulation breaks about an inch or so from the injector. It's hard to find and usually if you feel along the insulation, you can feel the break.
Also you could have a bad TPS (throttle position switch) on the side of the throttle body causing this too. It's a winding that has a sweep hand that senses the throttle position and relays this info to the ECM. If you have a worn spot at the common riding position, it could be the culprit here. Easy to replace.
You can test it with a DVOM (meter) to see if you get a smoothe reading while advancing the throttle.
There's three wires on it, one is ground, the other is 5 volts and the third is the leg to the ECM. This is the one you want to test to see if you get the smoothe reading as you advance the throttle.
