Tickover too high and hard to start when hot

Hi guys. I hope you can maybe help?
I have a mk1 GTI 1983 1.8
It runs very well but has always had problems starting when hot after about 15 to 30 mins. before or after its fine!!
It has also very recently started to rev very high. it goes down from 2000rpm when hot to about 1600rpm.
Any pointers please?
Injectors have been tested and 5th injector changed. Cold start valve is new.
Charlie

hot start issues can either be down to leaky injectors,  failed non-return valve in fuel pump or a leak in the system after the pump, if nothing obvious it may be the diaphragm in the fuel accumulator thats gone, to tell undo the wee screw on the end (if you can!) see fi fuel comes out.

check over the basic kjet stuff as per this thread, ignore the 16v bits
http://www.vwgolfmk2.co.uk/forum/viewtopic.php?f=37&t=25972

with the 1.8 ignition timing is set to 6deg BTDC usign the diamond as per piccy in thread above, but with vacuum line to dizzy disconnected and plugged.

with the idle, it may be the oring on the idle screw is worn allowing air to bypass and/or the screw to wind itself out. i used a one from a big box of various sized orings i got off the bay of e