Crap gearbox's (filler plug too low), oil consumption issues, bad coilpacks, timing chain stretches, piston rings, hugely underpowered. Etc not good engines. When SR20s and GA16s are so plentiful there's little point.
Mfactory are running a group buy at the moment for helical lsds and plated for the SR box.
An SR20DE with breathing mods will net you around 150-160hp personally I wouldn't bother with throttle bodies I would just get a VE head or engine then you will have 200hp no problem.
Yeah that will be the clutch, oiling the arm on top of the box won't do anything.
Its not hard to do just make sure you have enough time.
And clean and grease the bit the release bearing slides on, and the little clips this will ensure it stays nice and smooth and won't get crunchy.
Its all about driveability its not focused purely on top end.
The lower duration/lift lobes that will run out of puff at higher rpm switch to much bigger ones to make the most of the revs and the flow.
Its why my 1.6 N1 engine makes nigh on 200hp but the GA16 can only muster 100 odd.
Vvl uses different cam profiles (high & low) to open the valves more and for longer duration.
GA's have VTC changes the valve timing through adjusting the inlet cam.