Hi when the weather is cold the car fires right up first time, when I leave it in the sun all day it just turns over and starts the second time?

Impreza sti 2002 bugeye running 340bhp with green panel filter not sure about anything else as only had it for a couple of months. Thanks Marc

 

Fuel not staying pressurised, or pump slow priming?

Don't touch the throttle at all before cranking the engine and it firing.

 

Not sure to be honest, the first time it doesn't start no trotter pressed the second try slight depress of throttle and it starts?