Carb rebuild question

I've been fighting a rough, inconsistent idle for quite a while. I have done everything I know to dial it in including verifying timing, dwell, and using vacuum gauge to help set idle. No indication of vacuum leak either. I just can't seem to get it right and I know it's not just me being picky because I drove Timbob's 88 last weekend and it idles like a dream compared to mine.

When I turn the port side idle screw all the way in with engine running and in gear the motor stumbles but will not die. Screwing the starboard side in will quickly kill the engine. This leads me to believe the problem lies somewhere in there and something is just not right with the idle circuit.

I have a carb rebuild kit, but it seems silly to use it when everything about the carb seems great except the idle. Is there something else I should investigate or is it time to just rebuild?

The only thing I can add is, DO NOT look into the carb to see if you can see anything happening when using compress air into the passages. Gas really stings in the eyes. I know from experience. Put the air gun under a old tee shirt covering the carb. Or something like that.

if you have the kit then use it.
the rubber parts get dry rotted and stiff, o rings that seal the cross over tube also dry out and could leak at some point.

Its not a hard job so take it apart, use plenty of carb cleaner and or brake parts cleaner. and compressed air.   

Good to soak it since the gaskets for the metering blocks are tough to get off, carburator soak will soften them up nicely.