u've heard wrong. if it was that of a ad motor then why was toyota been using it since the 90's. the first 2jz motor that i saw was in lexus SC300 back in 91. there are no bad things about it unlike the 4g63 mitsu motors. lexus used the 2jz untill 05 in IS300 and GS300.
i've beed pushing the limits on these motors since 2000. even the non turbo motors can handle 550hp on complete stock motor and a good responsive turbo. i' never heard of any stories about 2jz being instant failures.
inj+injectors
comp= computer= ECU(engine computer unit) or EMS(engine management system.
harness= the complete wiring harness that goes from ur computer to ur engine.
in the jspec motor the computer is tuned to 440cc injectors. thus with many other things that require a complete different computer harness.
the engine block has been proven time to time. it can handle boost upto 60 psi turbos. that is a built block.
on a stock block i have pushed upto 27psi. depends on the turbo as well. 27psi on a mid size turbo is not the same as 27psi on a bigger turbo.
with the same boost small turbo i dynoed 470whp and on same boost level bigget turbo, i made 550whp.
stock twin turbos max out at 24psi in some cases. i ran 21psi on them.
also on the stock twin setup, the turbo is sequential. means smaller turbo(rear) spools at 2500rpm and max out at 8psi. the the bigger turbo(front) start spooling with the small one but makes the full bosost at 4500rpm. with the sequential setup i have not seen anyone making more then 19psi.
i bypassed my turbos. they spooled at the same time instead of sequential and boosted upto 24psi. all ypu have to do is change the springs on the wastegate to a bigger and stronger spring and bypass the valve on the rear turbo.
supra turbos are a bitch to work on. when i blew my stock turbos, i installed a bigger one.
it took me more then 24hrs of labour to take those turbos off and 1.5 hrs to install the bigger turbo.
all that include changing the turbo manifolds, some intercooler pipings, all the oil lines, wastgates, blowoff valves and some othetr minor stuff.
the only thing bad about the 2jz motors is to change the oil pump. in other cars its easy cuz its right there and u dont have to take any thing off except a couple of other shit.
on the 2jz motor, to change the oil pump out you have to take the motor out since its an I6 and every thing runs on one serpentine belt. so every thing is in the front of the motor. i've been doing that since a month. i took every thing out and then the weather gets too cold. it snows or freezes every other day. its -17 cesus right now.