a transmit problem with pf

[Yavuz Maşlak]

I have 2 leasedlines to reach to the internet.

I use 2 routers for these leasedlines. One of them is a freebsd7.2.

I activated pf on freebsd7.2.

I have a fileserver which has a real ip.
the fileserver's default gateway is other gateway server.
When a traffic comes from internet via freebsd gateway towards the
fileserver,  if I try to upload a file which has about 10Mbyte from a remote
pc to the file server,  file transfer performance will be very bad. if I try
to download a file from the file server, the file transfer performance will
be very well. it is no problem.
Or if I disable the pf,  the problem will be finish  and upload/download 
transfer speed
is very well.

Or incoming and outgoing traffic via my pf server ,  there is no problem.
on pf.conf, all packets are set as pass;
pass in all
pass out all
How can I sort  this problem out ?