upgraded to pgsql 8.2.4, getting worse performance then 7.4.x

Hello great gurus of performance:
Our 'esteemed' Engr group recently informed a customer that in their testing,
upgrading to 8.2.x improved the performance of our J2EE
application "approximately 20%", so of course, the customer then tasked me
with upgrading them. We dumped their db, removed pgsql, installed the 8.2.4
rpms from postgresql.org, did an initdb, and the pg_restored their data. It's
been about a week now, and the customer is complaining that in their testing,
they are seeing a 30% /decrease/ in general performance. Of course, our Engr
group is being less than responsive, and I have a feeling all they're doing
is googling for answers, so I'm turning to this group for actual
assistance :)
I'd like to start by examining the poistgresql.conf file. Under 7.4.x, we had
spent the better part of their 2 years as a customer tuning and tweaking
setting. I've attached the file that was in place at the time of upgrade. I
did some cursory googling of my own, and quickly realized that enough has
changed in v8 that I'm not comfortable making the exact same modification to
their new config file as some options are new, some have gone away, etc. I've
attached the existing v8 conf file as well.
I'd really like it if someone could assist me in determining which of the v8
options need adjusted to be 'functionally equivalent' to the v7 file. Right
now, my goal is to get the customer back to the previous level of
performance, and only then pursue further optimization. I can provide any and
all information needed, but didn't know what to include initially, so I've
opted to include the minimal :)
The DB server in question does nothing else, is running CentOS 4.5, kernel
2.6.9-55.ELsmp. Hyperthreading is disabled in the BIOS and there are 2 Xeon
3.4Ghz cpus. There is 8Gb of RAM in the machine, and another 8Gb of swap.

Thank you in advance for any and all assistance you can provide.
--
Douglas J Hunley (doug at hunley.homeip.net) - Linux User #174778
http://doug.hunley.homeip.net

Handy Guide to Modern Science:
1. If it's green or it wiggles, it's biology.
2. If it stinks, it's chemistry.
3. If it doesn't work, it's physics.