Powerbuilder to Informix - Poor Network Throughput

I work with a Powerbuilder application that talks IP to an Informix database across a network. I've noticed that result sets coming to the client across the network to the client don't utilize anywhere near the available bandwidth. INet is 5.01.WF1 and WJ2. Both behave about the same. I don't think ODBC is involved. Generally, across a very fast hardwired link, I get 2000 to 10000 bytes per second throughput, even though an FTP of the same amount of data cranks along at 500,000 - 700,000 bytes per second. I realize FTP will always be faster, but the difference seems ridiculous. Has anybody found any good ways to optimize network utilization??? Greg