Hey all. Nobody asked, but I've done a ton of mods to my 09 6MT sport/tourer. Here are my favorites as used in the DD/weekend tracker role.
For a rundown of all my mods look here:
Surfdog's 09 journal
#1 25 row Stillen kit Oil cooler. (great bang for the buck)
-track mandatory DD no difference
-Next time I'd probably go with the Z1 kit, but Stillen is perfectly fine
-DIY...maybe if your patient
#1a (Hard to quantify) All the stuff I fixed before it broke. most notably:
a. Zspeed CSC (OEM is crap)
b. Steering lock CB pull/recall fix (DD must do!)
c. DOT 4 Brake fluid (TRACK must!)
d. Hawk plus brake pads (DD no worries. TRACK must, amy race comp. pad will do)
e. max negitive OEM camber (track must to save tires)
#2 Quaife LSD (only if you drive HARD like I sometimes do)
-TRACK ...almost mandatory, DD awesome mod... if you drive hard
-Gets the power down in turns (the OEM VLSD is un-fun to drift/push hard) about 1500-2000 bucks installed but I'd do this before much else.
-definitely not a DIY
#3 Berk Catback exhaust (The sound makes you feel fast = FUN)
-Also a very doable DIY if you have an impact gun.
#4 Z1 400 hp kit (works as advertised and great bang for the buck)
-TRACK, better lap times. DD: not super noticeable, but sounds good
-All 3 bits DIY except possibly the exhaust manifold (its a bit involved)
#5 SS brake lines (very inexpensive)
-DD: no difference TRACK: very much improved brake feel)
-DIY definitely (caution don't over tighten)
#6 JWT lightweight flywheel, sport clutch. (expensive and a PITA to install, but makes the SRM sing and much improved throttle response overall)
-TRACK Works GREAT with SRM and Heal toe. DD no noticeable benefit
-not recommended for DIY
#7 Swaybars (I used Stillen) Some handling /roll improvement
-DD not really noticeable
-TRACK Very nice handling improvement
#8 Dynamat. (inexpensive easy DIY mod)
DD perhaps worth the time. TRACK NO WAY (Weight is bad)
-Some, but not a huge, noticable difference
In summary, I see a lot of guys going after big Hp gains and loud Exhaust. That stuff is fun too, but performance wise, I've gotten more out of Tires, Diff, and reliability mods (brake pads, dot 4 fluid etc)
Whatever you do, its all fun stuff! Half the fun for me is fixing all the weak stuff that breaks!
I hope this helps any new Z guys/first timers who might be looking at their build plan. I wasted a lot of time and a little money getting started on my build due to not really knowing where to start, but now I really love it!