suzuki intake and TB swap from 91+ to 89-90 car

[fixkick]

Oh and I forgot to mention I will keep my old 89-90 ECU I am not replacing that with 91+ ECU, I understand that it has completely another wiring.

yes I expected that , after all the harnesses are totally not the same, see my 89 difference page.
the same is true in the engine bay
like you stated and more. lots more is not the same
the distributor  and its harness is not the same and ECU 100% totally not the same. even cam shaft back end gears not the same, if you get my drift.
the injector wiring
the TPS wiring
and ISC wiring are not the same. and coil ohms 2x different.  89/90 is 6 ohms coil  and 91_ is 12.  so 91 will not damage the 89/90  ECU but may just be slow? IDK
the TB is not the same. nor its injector. (flow rates can be different on Gen1 to Gen2)

that 6 pin connector is based on the ABOVE wrong.

why not try to keep the same GEN1 TB.  if it checks out ok.  most are OK  unless the IAC fails the 150f hot water test or the iSC is jammped up or worse rattles like mad engine running as many do not, 30 years old. ouch. old.

not saying it can not be done, me, just saying that 6 pin must be wired right, pin for pin, and on the 89 the harness is not wired right for 91+ TB.
so wires must be cut and jumped

if you look close the 91+ has connectorzied ISC  and water heater hoses.
the 89/90 has no such thing, only 2 pig tails wired to the harness unlike the 91. with a plug.