I have a 2000 civic si its my daily driver but i am looking for more torque. I am surely going with a B18b block but i need help from people who have experience on whether i should leave in the stock ls pistons (all motor by the way) or get some higher compression pistons and do a lil bit of valvetrain work? Also should i run OEM fuel injectors or aftermarket and what ECU would be best for this?

 

ok for the LS/Vtec DO A SEARCH!!

but I'll cover some info for you

B18b
-Use the stock LS rods...but get ARP rod studs
-Get high compression pistons instead of the LS pistons. Get P30 pistons
check out this site
http://www.zealautowerks.com/

-so with that said you move onto the Vtec head whatever you choose(b16/b18c) head
-upgrade all the valve train and get aftermarket camshafts and cam gears.
You can get a port n polish done on the head and it will help air flow a bit easier into your and out of the motor.

There are many combinations you can do for LS/Vtec so I would suggest search for some of the best results