1999 BMW 318 Cold Start

The engine starts fine. When I pull away from cold the performance is very poor. It struggles to get up to speed. I back off and take my time, once the engine is warm everything is ok. I was also suffering from poor fuel performance. I have cleaned all of the air intake including the Mass air flow meter. Check pipework of any damage. Changed spark plugs, new air filter, ran petrol additive to clean injectors, cleaned carb. Checked all wiring to ensure that all contacts are good but still no improvements. Any ideas? It has been suggested to me by a friend that it may be the air temperature sensor.

Please help.

Regards

Jason Winch