Pre'96 ECU remap, non-vvti 3SGE Options

[quick_5hifter]

Hello everyone!
I have a '95 GT with the 3sge engine, no OBD2 connector. I've asked a few local dealers that do chip tuning/ ecu remapping etc. and they said there is nothing they can do to my ECU.
Before starting this thread, I used the search function, but nothing came up.

I want to keep my actual engine naturally aspired, so the only things I want to do are:
-cold air intake (right now I'm running on a K&N panel filter)
-complete exhaust (w/ headers)
-ecu remap (if possible).

I'm not considering a stand-alone engine management system, since it would probably cost about half the price of a Beams swap clip.

The question is: has anyone re-written the original pre'96 ECU's maps? If positive, HOW?

Thanks for all the possible answers, even if they're not what I would like to read