If it was the same solenoids that were running like cray, that could be explained by the high vacuum conditions created by having the car running (Idle) while in drive with the parking brake on. Engine vacuum is highest at that point, and only reduces once the engine moves off idle to higher rpms.
Your "X" relay is your ignition relay. If you think there may be something wrong with the relay itself, you can swap it with the XVI (Horns) relay and see if there is any change. If the swapped in relay acts the same and your horns work, the problem is elsewhere. (Be sure to check for any corrosion or oxidation on the terminals of the relays and clean before installing though).
I'd need a refresher myself on what harness runs through in the area of the smog pump, so until that happens, maybe someone else will chime in with that info. and what could possibly be effected by it's wiring possibly being shorted.