Doesnt sound normal to me.

Lots of people do the power antenna override mod as its a pain if you dont want to listen to the radio, but the radio shouldnt come on as far as I remember (been many years since I had a standard H/U!).

Well done.

Will you be testing the new set up once fitted to see if the problem has definitely gone?

You might get an indication by getting the engine fully warmed up, let it idle for a minute, then BOOT the throttle, easier with a helper to see the exhaust output.  Well done in persevering.

  good work to find that out with some patience involved as well 

I'd be inclined to leave it out.

Does sound a bit odd.

I had a similar issue with my standard radio turning on by itself but mine wouldn't even turn off with the power button. I replaced it with one from eBay - a relatively cheap and easy fix

Yesterday we fitted the Toyosport manifold and new main CAT and it now revs properly.  Clearly that was the answer all along, the pre cat in the right downpipe had completely disintegrated and blocked the main CAT.

I guess the question now is whether bits were also sucked back into the bores giving us a car with a serious oil drinking problem. On the face of it the engine seems ok.  On start up there is lots of steam but after a few minutes it seems to run clear and idles smoothly.  I'm hoping the previous owner experienced a catastrophic CAT failure event which rendered the car immediately undriveable such that bore damage was limited......is that even possible?

I guess that we wont know until we get the car on a road test and we are currently a long long way off that.  Suspension, brakes and power steering all need an overhaul plus misty headlights and some rust issues.  I'm sure I'll be back on here asking more questions soon. You lot are amazingly knowledgeable, thanks so much for sharing your wisdom.

Well done for perseverance.

The standard radio in my 2003 roadster always turns on and raises the aerial when the ignition is switched on. If I turn the radio off, turn the ignition off and then turn the ignition back on, the radio will turn on and raise the aerial.

Is this correct or do I have a fault?
I would have thought that if I turn the radio off it will remain off when I turn the ignition off and on again.