by Bennis » Mon Aug 01, 2016 7:15 pm
Going off your profile Im taking you have a GT liberty? If so then raptor headers will not suit your car, as they are designed for the n/a ez30 flat 6 (second version).
I think the general consensus with any turbo flat 4 subaru setup is that the stock unequal length headers/exhaust manifold are fine until you have maximised all other logical upgrades (turbo, fuel, etc).
Being that yours is a 2007, you should have unequal length headers. So leave them be and just upgrade the rear mufflers if you only want a sound upgrade for the classic subaru burble, or you can go for a full turbo back exhaust for sound + performance upgrade. Keep in mind a tune will likely be needed if you go for a full upgrade (someone who owns one could probably confirm that).
If you happen to still insist on changing the exhaust manifold, changing to a different unequal length aftermarket manifold will keep the subaru burble. Changing to an equal length aftermarket manifold will mean you will lose the iconic 'subaru' sound, and it will sound more like other turbo 4 cylinder cars, e.g. Evos/ Silvias/ etc...
Changing the headers to either unequal or equal length and leaving the stock system on will make virtually no change in the sound level, only a change to the note of the exhaust (should you go equal length) .