Sounds like an intake tube to me now. If you already found a hole there is probably more there than meets the eye. Mine cracked on the bottom side and caused havoc until I figured it out. Have you lost any power or just poor idle? It caused me to lose alot of power though, that's why I'm curious if overall performance is being effected.

Check your O2 sensor w/ an ohmmeter, otherwise I have an extra intake tube lying around that I can get rid of if needed.

My list of trouble shooting would go like this, intake tube, vaccuumm lines, vsv's, egr, O2 sensor, tps, mas, then I would look at the fuel system, pressure regulator, overall pressure, return, etc. I would think that the problem lies somewhere in there but if not, the ecu, or maybe even the intake and plenum gaskets sprung a leak, who knows?

Is the overall performance effected or just idle?