Tuning question

Hi guys and girls
I have followed your forum for a while now and listened to a lot of advice given And have decided to sign up as I have questions and am finding myself using this as my personal bible lol.

I've owned my mr2 now since late June; bought it from a guy who owned it for ten years and by the looks of it he was very devastated by having to move it to a new home. I am extremely pleased with it, also I'm from Newcastle.

I have been in the process of doing a few minor upgrades and has come to the point of having a piggyback installed and it tuned

Mods so far have been:
Weapon r secret Cai

2.5 inch 100 cell hi flo cat

2.5 inch mandrel bent catback with hi performance muffler into dual 3 inch tips

Innovate wideband gauge and lc1 lambda cable/sensor

8.8mm top gun ignition leads

Nissan r32 gtst/gtr staggered wheel setup
And running royal purple oil

About to purchase (within a week) Megan racing coils as those have been the best for the price I have found unless someone recommends
different

My question is
I have bought a second hand first gen apexi safc the one with the dials for 80$ with harness and manual
Is it worth installing this and tuning or should I get turbo injectors or fuel pump or would it be fine on the modifications listed also how much power would an approximation be in terms of gains
The car is a 1990 Toyota mr2 N/A

Any help would be appreciated
Thanks :)

Is there a reason why you wouldn't bother with the safc?
My reasoning for using it relies on this:
They come factory quite lean running as most cars do
My afr gauge reads about 15.8-16.8 throughout rev range and on WOT drops to about 15.3; stoich is 14.7 if I remember correctly any higher is lean and lower is rich from what I have read most na's get the best power at about 12.8 with i-h-e mods done, even stock cars have seen gains

I was just wondering if it makes more sense spending the extra few hundred on used injectors and pump or just have it installed as is and a decent tune?

Also from what the people I've spoken too 2.5 inch is fine
(
for an mr2 being a 3s however I was warned it would be quite loud haha
:)

For the exhaust I spoke to a guy with years of exp with mr2s in Queensland and he recommended my current setup if I wasn't worried about the noise, and also there was a thread on here backing that up as well

But yeah it is quite lean
Sorry It was meant to say drops to 14.3 on wot
But yeah I've heard of them leaning out turbos

The wide band is located forward of the cat just after the b bend from the factory headers

The guy in Queensland didn't own an exhaust shop owned a dyno shop he just knew mr2s inside and out

But I can tell you the Newcastle shop that did mine
Cost me 300 for the cat back including stainless tips

Update after new exhaust it's settled down now no idea why but since the cat and exhaust its been sitting around 14.7/13.5at wot in 3rd so that's a lot better