EE9 - OK, that sounds like a catback, meaning its from the catalytic converter to the end of the car. Pretty good stuff. The performance exhaust should give you a better exhaust flow and a noticeable increase in hp.
S9 - Got no intention to change or add ECU at the moment or in the future (of course, this is the sensible side of me talking here). This is what I know abt ECUs, I ain't no pro but from what i've been told....changing the ECU usually mean that the mods to your car requires re-tuning of the air/fuel mixture etc. These mods include a varied of things; increasing boost, changing to a bigger turbo, change gear ratio, change camshaft, ported heads, da da da da da and da so the list goes on. I know that the HKS F-COn V Pro is a fully programmable piggy-back system and is extremely desireable. If money is not an issue, most race cars uses the MoTec M800. The M800 is the authority in ECUs. My 2 cents.
p.s. If I every install an aftermkt ECU, you know its the bad side of me taking over. Sometime I can't help it when Dr.Jekyll takes over... hahahaaaa.