Just to follow up, i found that the plug connector going to the coolant temp sensor was rooted and when you pressed on the plug whilst the engine was running, the fans would come on and the car would run really rich.

So i replaced the plug connector, and cleaned the crank angle sensor the best i could and now the car doesnt hesitate at all, hot or cold. Sensor has since been replaced with a new one for good measure

As for the hissing noise when switching the car off, i found the hose going to a heater? vacuum solenoid had come off, fixed that and car doesnt hiss anymore.

so wouldnt the faulty coolant sensor plug have given a bad reading to the dash as well???

did u replace the crank angle or the coolant sensor??

yes replaced both in the end, but the coolant temp sensor's actual plug was playing up.

Funny thing it never played havoc with the gauge, but when you pressed on the plug lightly the engine went beserk and thermos came on, and ran really rich, so was replaced with another plug, and this one is fine

how strange