engine sounds terrible

[Jason Nicholson]

OK, my engine has really started to sound like crap
over the last week & as a result I'm tried to drive
the car as little as possible until I drop it off at
my mechanic (Phoenix Imports) tomorrow morning.  It is
a '99 Sentra SE-L w/ JWT pop-charger, JWT S3 cams, HS
gen.4 header, & Stromung cat-back exhaust.  There are
about 72k well driven miles on it.  I did the standard
tune-up stuff last summer: distributor rotor, plugs (I
used Bosch platinum +4), stock wires, & fuel pump.  It
sounds really loud in the lower rpm's, kinda like a
car with a muffler that is about to fall off, but not
quite THAT loud, and the idle is not very smooth
either.  The noise is coming from the back side of the
motor, near the fuel rail, fuel injectors, etc.
Anyone have any ideas that I can look into my self
tonight?  I would greatly appreciate it.  I hate to
see a loved one suffer.

Jason