One thing I noticed when checking the dash lights is that my indicators were flashing too fast for IVA.
This is due to my indicators drawing less current than the MX5 ones and cauing the flasher to think one of the lights had blown.
The usual solution is to add ballast resistors, but it's not particularly elegant, and by the time I noticed I'd already taped up my wiring loom and didn't fancy chopping into it again.
After a bit of googling I found this site which details how to modify the MX5 flasher to work with LED indicators:
http://forum.miata.net/vb/showthread.php?t=335534
All it involves is swapping a resistor (hope the guy doesn't mind me nicking his picture):
In fact the mod was even simpler than that; all I did was remove the resistor and not bother replacing it at all.
I figured a 1Meg resistor probably wasn't doing much anyway so tried without and it worked just fine :)