not just the engine, change the diff to a 3.45 ratio, phase 2 or 3 cam, guy on www.boostedfalcon.com
has definition files and j3 adaptors for ef and el 6 cylinder.
i like lukey headers but most people go for jmm or pacemaker etc or
supercharged / turbo charged is always kewl.
aftermarket fuel regulator ramped up to 300 or use xr rail regulator.
port head and plenum
if you want to increase speed limit, you should install a driveshaft loop as fords tend to spit drive shafts at higher speeds.
ive got a 75hp zex NO2 designed specifically for injected engines, (aswell as supercharger)
get an O2 sensor like innovate put out so you can make sure you dont run lean.
if you go supercharger or turbo, dont overlap your cam profile. stick to 114.
better coil would help and if you generate enough power, you should seriously look at a better fuel pump or even a surge tank setup.
if its boosted, put in an oil catch can,....do it anyway now i think of it.
no bigger than 9 inch rears, and go lsd.
if its auto, 2500 high stall converter.
with boost or nitro, you should change spark plugs and gaps.
with high performance cam, get a vernier cam gear to fine tune.
there may soon also be a 4.8ltr stroker kit as a company is currently working on it and trying to get it produced overseas.
the head on the e series i6 isnt that great, so high rpm is a bit of a mission, i personally thing making use of its low end is a good idea, and let it max about 5500 to 6200.
electric water pump reduces loading on engine during short bursts, and high octane fuel is always a bonus.
check connection to your stepper motor on the throttle body in relation to the rpm issue