Si2k

Sounds like the yellow box speedo fudge is not done properly, all the issues you are reporting are due to the speed sensor.

•Speedo gets a mind of its own. It will read numbers at random and today it even stuck on 0 for a large part of the day, even when doing 130mph+
•Petrol gauge has a mind of its own.
•Check Engine Light is coming on sometimes and wont clear. Pulled the code, P0720, 'Output Speed sensor unit' is the fault.
•Steering wheel light and '!' next to it is coming on some times.
Car won't rev past 6 or 7k approx occasionally.

- Speedo sensor signal messing up
- What's new - petrol guage doesnt help
- CEL confirms speedo signal
- EPS relies on speedo signal
- ECU thinks the car is stationary, it wont allow VTEC and limits revs when the car isnt moving.

It sounds like the yellowbox is the cause of your problems, probably a lose connection or something.

Tegiwa Imports

Has your fuel pump ever been out? The senders can get knocked off their mounts pretty easily putting them back in, this results in the readings being all over the place

zzkamikazezz

Yep, going to try a new yellow box and get the wiring looked at. Hopefully its just that.

The fuel gauge was an odd one though, I've never seen it be so erratic. The fuel pumps never been out.

Thanks for all the suggestions, I'll report back after I've had the yellow box looked at