-Make sure that you are definately getting spark at the end of each leads.
-Check leads are in the correct sequence.
-ICM has given up or rotar button may be worn out.
Ive recently changed my front EG hubs with brand new wheel bearings a couple days old BUT today came across a pair of DC2 hubs/rotor/calipers for a cheap price for an EG brake upgrade....
Ive used an EG3 Breeze radiator for a B18C with no issues.
Check thermostat as mentioned above ^
After coming home from a drive leave your car on & stationary, then inspect that your cooling fan...
Have you checked the Stop.Horn fuse in the fuse box? Its located in the engine bay.
Might be as simple as that for the horn not working, but then again your Brake lights shouldnt come on as well if...
Regardless of your car being low or not, the wheel arch liner will always act as a sort of protection/barrier between your filter and the ground.
Just go with what "Thesaint" mentioned above, as...