So, I went to day and updated my L61 Header and Downpipe to an LSJ. I've seen alot of posts about this being "a cheap upgrade mod". And it is. I got my Header and DP for $125, and with a little machining work to the studs, and all new Gaskets, I have $200 in a better exhaust.
There are some major differences between the L61 and LSJ Header.
DownPipe: Flange to Cat:
Downpipe: Cat to o2 Sensor:
Downpipe: After O2 Sensor:
Header to Downpipe Port opening
L61: 1.9" x 1.6" D shaped
LSJ: 2 1/4" Round
LSJ to L61 Downpipe:
It sounds louder and lower exhaust note. This is hooked to a GMPP Cat back.
I will be dyno'ing the car Saturday, at which time I will be able to list whats gained, as my car was last ddyno'd in April, and this is the only performance mod since then.