Okay I’m getting a JDM b16a. Now I want to build it up. (Cams, pistons, etc.) What I want to know is what OEM parts would fit correctly. ITR or CTR? I know ITRs are b18 and i think CTRs are b16. (Correct me if I’m wrong. Still learning. 
) So since its a b16a, should I go with CTR, or would ITR parts work as well?
CTR and ITR pistons will work. The CTR pistons will give you a higher compression ratio. CTR cams are more agressive than pre-99 ITR cams. That’s about the only meaningful differences.
Generally speaking,
A complete and original JDM CTR engine has a smaller displacement block, but with higher compression pistons, higher lift and duration camshafts, and a well breathing head.
A complete and original JDM ITR engine will have a larger displacement block, with a less lift and duration camshafts. Also, the compression is lower on the ITR compared to the CTR.
IMO, go with CTR parts.
go with a tech43 piston/rod kit. its when u use the b16 block and go with a either 82-85 mm block and run ls crank and ls length rods with a custom arias piston wit the correct valve reliefs. yes theres alot of machining for this to take place but imagine the power and i did a price list check on this once b4 and it was going to run me about 2000 in that range.
if u wanna do just a reg mild build tho i suggest when u do the CTR pistons and cams to just go with a slightly bigger than ctr camshaft. maybe even just a set of skunk2 stage 1’s and a IM and TB
$2000 in just parts or with machining and labor…or are you saving by doing ur own labor? how much is the Tech43 stroker kit?
i forget the exact amount that it was going to cost but i priced out a whole sheet b4 on it by my machine shop guy and its was around 2000 alltogether for a sick decent setup. mind u i would proabbly upgrade to larger cams also(at least CTRs) but with the 85mm version of the stroker kit it puts u to a troo 2020cc engine. just look it up on HT if i find the thread i will link it here.
Okay so both ITR and CTR pistons will work. It sounds like CTRs are more of what I’m looking for. Now eventually I will want to add turbo to this engine. So what would I be looking to rebuild, reinforce or change in order to get a decent amount of boost?? Would the CTR pistons and cam be good? And what other parts would need to be swaped?
ctrs will yeild u higher compression for ur b16 which isnt necessarily bad but it isnt the best option yet. if u plan on building for turbo i would change ur cams and build the head for more power for boost(ie.- itr/ctr/or gsr cams/ skunk2 IM and itr or aftermarket TB). and add a thicker headgasket and headstuds stay wit ur stock pistons also. if u wanna build for all motor with ur b16 i wouldnt replace it also with itr pistons, b16 pistons actually yeild higher comp for ur motor and itrs will lower ur comp. which is good for turbo but yet why use cheap non forged pistons when u could just rebuild with forged while its all apart.