Check out this link for the US Spec. part numbers.
zer...D.pdf
In the US, the preferred TCU is from a 1993 model year Q, ending in 64U20 or 64U75, but I don't know what the corresponding part number in JDM land would be...
In the US, the 90-93 all had the same gearing in the transmission, but only the 1993 model year had the 1st gear start TCU. The 1994-1996 transmission had different gearing. Many members have used the 94-95 TCU on a 90-92 Q with good results, but to be technically correct, the 1993 is your best bet because it was the only one designed with your specific transmission in mind.
Good luck!
Heath