Very unlikely to be a ECM(ECU) fault unless cause d by shorting wires.
The TPS does NOT control the throttle cable, it relays info about how far open the throttle(position) is to the ECU the ISCV or idle speed control valve opens the airways via a seperate passage to admit air for starting AND for low speed running, the TPS do sometimes lose their tracks inside and idle track area is a fav to suffer so would be worth trying another, you will soon know if this is the case as the idle when hot will be a bit hit and miss and it will be lumpy too, but fine when cold, the TPS when it signals a closed position enriches the mix slightly at idle to give smoother idle, when it is missing the "closed" signal it of course does not richen and you suffer a "lean cruise mixture", which is much weaker than a idle mix needs to be.
If you phone WEBCON up they will tell you the best place, for cossie bits I use MATT LEWIS 01922 692424, he may be able to get you one if noit WEBCON are on 01932 788805.
WEBCON + WEBER one and the same and now include MAGNETTI MARRELI.
tabetha