My Engine Warning Light has Started to come on causing rough running and idle, I am given to understand that this could be caused by the O2 sensor & the ECU being faulty, If this is the case what is their location on the car that I may change them.. 1987 MK11 Turbo Supra.. Thanks and I will Wait For a Reply

O2 sensor is bolted right into the elbow behind the turbo

ecu is behind glove box .
it would help if you pull the codes the engine light is recording
heres how

i would check the two (vsv) valves on the intake side uder the intake one is for fuel one is for EGR
both are vacuum switches
you might have a diagram of these 2 switches on the underside of the hood

you might want to check out these service manual pages
EFI troubleshooting
diagnostic
if it's a california car there more O2 sensors