new to the forums so I know my credibility isn't worth a hoot but I just would like to chime in if that's ok. if 300 hp is where you want to be at the stock ge will take it all day long with a proper tune as mentioned above. your fuel system is the life blood so don't cheap out there, you will probably end up spending more money on that then anything else but it is the key. you could buy a cheap ebay turbo kit and if the turbine failed the you lose boost, just have to change turbine. your fuel system leans out then well you wont only grenade your engine but could potentially cause injury or worse.
with that in mind here is just a couple of the more common builds we have found over the years of trial and error that has saved some brothers a bunch of time money and headaches.
even for the 300hp range I still recommend stand alone, wire in parallel and keep all your factory functions, as you will find in a search because it has been mentioned numerous times when choosing a stand alone it is best to consult the person who will be doing the tune. our local tuners still like the aem v2 but I hear great things about haltech and ecu masters. good quality fuel injectors and fuel pump. we have cars that run oem supra fuel pump and 440 injectors, though the AEM stealth is a great alternative, dont like walbro so much but thats just an opinion from years of experience with them.
as for the motor in this power range leave it exactly how it is. yes do a run through make sure everything is ok compression test and such but no need to separate the head and the block. contrary to what some may say the ge vvti rods will handle this amount of torque. no need for head work either "the stock motor is fine"
now a turbo kit LONG SSTORY SHORT.... best bang for your buck we find comes from CXRACING. they have a complete bolt on kit for less then 2k. thicker manifold option as well that seems to hold up, none we seen have failed yet. weak link we find is the wastegate, spend the money and get a good quality wastegate tial or turbosmart is what I recommend, the blow off valve is a cheap kinda one also so get a better quality one when the time is right. or you can look for and shave down the imperfections you come across s it does not get stuck, the choice is yours.
I probably missed a couple of things but that's pretty much in a nutshell what we do for the guys wanting to be at the 300hp range reliably daily driven.
now for the guys wanting to hit the 400+ range the set up is pretty much the same as the mentioned above except we do work to the motor. only thing we UPGRADE if that's the proper word are OEM GTE rods and OEM GTE headgasket. that's the only things needed to allow your ge to reliably hit this hp range. however we always recommend changing all the bearings, piston rings, going with arp studs, valve stem seals the works. last thing you want is to have done all this work and have an old main bearing fail or old piston rings go.
at this point it pretty much blows the budget so to say but we recommend you send the head in to get some porting done, whatever you can afford, horsepower is an addiction and if you already have the motor apart just get it all done now to prepare for the inevitable, unless you enjoy taking your engine apart all the time then more power to you lol.
anyways this was just some ideas to throw out there, it is in no way shape or form the right way or only way, these are just our experiences we have with the 2jzge. there is much more we could elaborate on and get specific with but I wont continue this novel to an epic trilogy. if you do have any questions feel free to send a dm, always enjoy talking and learning 2j with people.
"why yall keep smellin your arm pits???"