I previously posted a message about an poor idle/stalling problem, but that problem has grown to a constant misfire at all engine speeds, in addition to the poor idle and occasional stalling. It's a 93 245 with 118,000 on the engine. I'm the second owner and have had it for about 5,000 miles. It has the LH 2.4 FI and the EZ-116K ignition, no EGR. Here's what I've checked/discovered so far:

1. No codes from either the ignition or FI (sockets 6 and 2).
2. Car never had the O2 sensor replaced, so I replaced it w/ Bosch OEM.
3. Spent about an hour checking for vacuum leaks using soapy water. None.
4. Used the Bentley proceedures to check the throttle switch, air control valve, and air mass meter. All within spec (according to Bentley).
5. Spark plugs seem to have a bone-white deposit on them (or are burning lean), but gaps are correct. This made me suspect that it was burning lean due to a vacuum leak, but can't find a leak.
6. Replaced a hard plastic vacuum line from the charcoal cannister to the throttle body that was cracked, but this port doesn't produce vacuum at idle.
7. When I turn on the A/C, the Bentley manual says the idle speed should increase, but it doesn't.
8. Fuel pressure checks out OK.
9. Replaced cap and rotor. Wires seem good - all have the same resistance, about 3400 Ohms.
10. Cleaned fuel injectors off the car - good spray pattern.
11. Main ignition fuse in engine compartment is OK, but the fuse holder is slightly melted under the ignition fuse. Don't know what caused this, but the fuse itself is making contact.

Any ideas? Thanks.