Good for you, knew you could do it with a few o-rings and bit of patience.

As for chronic idle/stalling with a B234F, well I'll tell you right now you have my sympathy as they are indeed more sensitive to such problems than the other red blocks. As much as anything, idle/stalling problems with my B234F are what first brought me here to the brickboard well over 20 years ago now.

I'll start off with a few B234F specific thoughts for you that can affect smooth idling on the ignition side. Make sure there's no oil down in any of the spark plug recesses from the inner area of the valve cover leaking so that oil vapour doesn't foul ignition wires. Make sure the ignition wires are in good clean shape, solidly on the plugs and in the distributor cap and coil, replace as needed. Keep underneath the plug cover plate clean. Most importantly, make sure the plugs are in good shape. On the B234F (geared with the AW72L and different rear end ratio) during lots of low rev city driving the plugs will more easily foul. Cruising along at 1600 rpm isn't what these engines enjoy. Using nothing but high octane gas with premium additives definitely helps -something cheap people like me have problems adopting. If giving it a high revving Italian Tuneup makes a significant difference for a few weeks then concentrate on fouled/worn plugs as being an issue. I found switching to a slightly hotter spark plug reduced fouling for me as I did mostly city driving at the time. The early production 1989 coils used with the B234F were also known to be a bit weak that created spark problems, but by 1990 yours should not be an issue.

Now on the intake side, and this is where you're likely to find actual stalling issues, make sure the entire intake and PCV side is kept scrupulously clean, no vacuum leaks and everything is adjusted to spec. Beyond spark plug fouling, a lot of my idle/stalling issues were related to a dirty throttle body and incorrect adjustments (some were my fault, trying to raise the base idle to get above a rough idle). A dirty/sticky/worn IAC valve makes for a bigger issue with these more sensitive engines. The Volvo specs for the B234F throttle linkage adjustment are actually slightly different from the ones you'll see here and elsewhere for the B230F/FT, but the principles are exactly the same and the specs are close enough for practical purposes.

If you're interested in a recent discussion I've had here on idle/stalling issues and throttle bodies, you may want to check out this thread for more hints TPS Sensor test 700
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now