I've been searching the past few days on the most common mods for M35's. So far ive come up wth these. There are a decent selection of parts to choose from, but obviously not as much as your more common imports.
1. Intercooler kits:
Blitz - no
HKS - no
ARC - available but bloody expensive
Trust - V and R-Spec kits available.
2. Exhausts
Blitz - no
HKS - yes, Demoda
Trust - no
Fujitsubo - yes, few models available
Kakimoto - yes, Hyper Mega N1+
Tanabe - yes
3. Intake kits
Blitz - yes, Sonic Power
HKS - only for VQ35DE motor
Trust - yes, Airinx
4. Coilovers
HKS - yes, Hipermax LS+
Cusco - yes, Zero 1, Zero 2
Tein - yes, Basic Wagon, GT Wagon, Super Wagon
Tanabe - yes
Aragosta - yes but hugely expensive
JIC - yes
GReddy - no