cold start acceleration prob on audi coupe 2.3e

[smicker]

i have an 1990 audi coupe 2.3e 5cyl ng engine. when the car is started from cold it has to sit and idle for about 5mins before trying to rev the throttle. if not left to idle the car the car will drop a cylinder and will stay like that till it reaches temperature. also if revved when cold the exhaust whistles. this only happens when cold.the oil pressure gauge when cold indicates maximum oil pressure and stays like this till engine is hot and then it reads mid way.tappets seem to rattle until it reaches temp.when the car is up to normal operating temp the car runs well.

any ideas

thanks
smicker