responding out of the same gateway as the incoming request on same subnet

responding out of the same gateway as the incoming request on same subnet

i have two different ISPs with NAT routers connected to the same subnet
192.168.2.0 that has a Centos6 server with 1 nic at 192.168.2.200. the
gateways are GW1 192.168.2.1(default) and GW2 192.168.2.2. any connections
coming in on GW1 are connecting fine. any connections coming in on GW2 are
not connecting at all. If i change the default gateway on the server to
GW2, then connections from GW2 are fine and any from GW1 now no longer
work.
i assume packets are being routed back to the default gateway, and being
dropped because the NAT is from the other gateway.
how can i setup rules to route incoming connections back via their entry
gateway and not use the default route.