1998 BMW 328 Blower

My 328I"s a/c does not seem to cool very good. I have the proper amount of R134 in the system and there does not seem to be any leaks. Also the fan does not blow very hard , even on the highest setting you would not want to be in the back seat. It just does not cool the interior of the car very well. Any ideas on where I should start
thanks Pat