Hi IBMapc,
Glad you managed to get that nice motherboard working, I have a few 486 MBs myself. Regarding the IRQ issue, if everything's working ok I wouldn't worry about it in the least, those diag programs aren't perfect. When I used to use AMIDiag, a diag program used by DEC / Digital Equipment Corp on their Celebris etc computers, oftentimes it found errors with the CMOS, or Y2K compatibility (testing it in 2002, what's da problem lol) or whatnot, was just the computer being different or too new etc. Actually I've rarely seen IRQ1, being real basic and always for the keyboard it's kind of not shown by software most of the time.
Hope this helps, cheers!
Bellarmine