Hi, friends in PIC circle, I realy need your help!

I am doing an experiment using a P16C56 to receive FSK Caller ID
signals. Now I think I have done most of the work, but the test
shows that the reception is not good enough, i.e. too many error
results!

In my programing, I ignored the CHANNEL SEISURE signal sand after
detected the MARK signal I let PIC receive the Hi's and Lo's on a
pin connected to a FSK decoder with a quite precision timing to
recover the serial data into bytes.

Well, as I have watched the signal with a scope, I know that it is
usually mixed with noises,so even an accurate timing for sampling
the signal can not assure a correct reception!

I think I have tried hard to improve this, unfortunatly, I am only
a newbie in PIC circle and have no experience in dealing with FSK
signal.

I hope you can give me help and advice as much as possible.

Thanks in advance!