heh
well obviously it would have to feed somewhat evenly to all 4 cylinders or else honda would have a problem on their hands

its located by the thermostat housing but its on the intake manifold, looks like a big mushroom (bronze colored, black plastic top) with a 3 wire plug and 1 vacuum line coming out of the top of it.
ill make it easy, heres a picture

look, you would get an EGR code of some kind if this was the problem, maybe it is, i dont know but when my valve broke, i got a code and the engine ran like shit, maybe check the distributor and associated timing sensors, cause im pretty sure it can only detect #1 cylinder misfire anyway, not the oher 3.

did they test or replace the spark plug wires? i had my #1 cylinder wire fail the other day (see related thread )

let me know

~boomer