Which pulley did you change? The alternator pulley? To a larger or smaller one? If you changed it to a larger pulley to try and increase horsepower, you're pretty much screwed in terms of alternator output. Lost amp output at idle is common-knowledge amongst people who get an under-drive pulley. You can't "have your cake and eat it to" in this situation.
But, besides that, the ECM controls the idle, and there's really no way around it. If you had a scanner, you could see something called "DESIRED IDLE RPM" that is constantly being adjusted by the ECM via the IAC Valve based on the current engine temperature(the hotter, the lower the RPMs). You can try adjusting something called the "Idle Stop Screw", but it's HIGHLY recommended that you do NOT touch it!! Anyways, if you do adjust it, the ECM will just respond by lowering your IAC Counts, and therefore will lower the idle what it wants. So even adjusting this, which you shouldn't, really won't make any difference. The ECM is the commander-in-chief here.
So, in conclusion, the ONLY way that you could possibly do it is to get a PROM that is programmed to command a higher idle RPM at every engine(ECT) temperature. I'm not sure if they're available, but if you had a PROM programmer, it's extremely simple...