how much tuning before ecu needed

[koh]

ok so ive done a search on tuning the 4age,both here and toyota owners club,and i dont feel ive got much useful info as far as the ecu goes

i want to play around with the standard engine in my car while i consider future engine swaps

ive got new leads and plugs,cambelt and waterpump changed,apexi filter intake cleaned
might get one of those obx exhausts and manifolds(wrapped) as mine is knackered and i dont want to pay 500 pounds for a buddy club back section,prices on exhausts are silly over here!!,decat pipe is ready to go on.
alloy alternator and water pump pullies have been ordered,viscous fan is coming off for an electric one,engine has 136km under its belt

will the above mods free up much power or do i really have to get cams before it livens up?

at what point on the std 4a does the ecu need replacing?