Difference from Stock ecu to aftermarket ecu

i was wondering how much hp i could possibly get if i got an aftermarket ecu and tuned it. if so, it would be the Link g4 ecu, and then dyno it.
Even thow i have minimal upgrades, there should be some horsepower gain?

Specs:
Celica 91* ST185
Stock air to air intercooler
Upgraded to a bigger single wastegate turbo "S148 Hybrid" (gt4-play)
3" DeCat downpipe (gt4-play)
Cheap HiFlow Muffler
Running on 1 Bar boost
AEM AFR Gauge

going to get Forged pistons and rods, and get a steel headgasket

Depends entirely how good the person tuning it is, how good your fuel is, etc. If they don't know the 3SGTE and they don't know how to use a Link you can end up making less power than stock. Pick a tuner, then see what ECU systems they're familiar with.

underscore":2ignte68 said:

If they don't know the 3SGTE and they don't know how to use a Link you can end up making less power than stock. Pick a tuner, then see what ECU systems they're familiar with.

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Agree! You can go buy a Syvecs to have every option in the world but if all anyone (around you) knows is Haltechs then you'd be better off with that (not knocking on Haltech, I have one).

ok, i see. but what if i chose the right system at the right tuner. what numbers are we speaking? how much hp ca?
i probably have around 250-280hp now.

Depends on your elevation, fuel, temp & humidity during dyno/tuning session, type of dyno being used, etc...too many variables.

Based off your list of mods though, I suggest a nice adjustable fpr, larger injectors, new fuel pump, and a wta or fmic before tuning it. The tmic and fuel system is going to be your choke point. Then you also have to plan if you'll be running e85 then you'll need to upgrade your fuel system to be able to handle e85 and get another tuning session done for e85 only.

My recommendation, look for a complete standalone that gets rid of your MAF and uses a map sensor because the MAF is going to be your next choke point in making a lot of power.

You'll have more hp and more reliability but the cost to enter will be significant. After parts purchase, new sensors, any rewiring, and dyno tuning will set you back at least 2k USD.
It's only worth it if you have a bigger turbo. With the ct series I'd suggest just getting a jdm ECU if you want to many any changes.