How to force PostgreSQL to use multiple cores within one connection?

Hello.

My application generates a large amount of inserts (~ 2000 per second)
using one connection to PostgreSQL. All queries are buffered in memory
and then the whole buffers are send to DB. But when I use two
connections to PostgreSQL instead of one on dual core CPU (i.e. I use
two processes of PostgreSQL) to insert my buffers I see that things
goes 1.6 times faster.

Using several connections in my application is somewhat tricky, so I
want to move this problem to PostgreSQL's side. Is there any method
for PostgreSQL to process huge inserts coming from one connection on
different cores?

Thanks.

--
Sergey.