Code P0508, high idle, exhaust manifold turns orange

Hi, I bought the vehicle listed above with a stripped engine. Reassembled the engine with new rings, bearings, mains, thrust washers. New timing chain, oil pump and water pump also. The head went to the engineers who determined that there was nothing wrong with it, new valve stem seals fitted and skimmed lightly.

After assembly fitted engine into van, van starts on the turn. Idles at about 1,300 RPMs and the exhaust manifold glows orange.

Cleaned injectors using carb cleaner, scanned the vehicle using Forscan and produced the code P0508 - Idle Speed Actuator short to ground. Replaced the idle control valve and started the van, still idling at 1,300 RPMs and exhaust manifold turns orange / red.

I did a fuel pressure test and at idle the fuel pressure is approximately 2.3 bar. The Bantam specification says that the fuel pump is three bars, unsure if the 0.7 bar would cause the exhaust to turn red / orange and also cause the idle to remain consistent at 1,300 RPMs.