TF: Typical Micromaster car: fold the back of the car back to become the legs then fold the bonnet back, stand up and bend the arms at the shoulders. That saves my typing - just Copy & Paste it !
Robot mode reveals a yellow head, body & upper legs with the bonnet hanging behind him giving him some stability issues. The revealed yellow is quite a nice choice - Circuit isn't the first Transformer to be known by that name. One year previously Actionmaster Circuit (a repaint of Axer's Action Master robot) had been a European exclusive. Action Master Circuit looks like he would have transformed into a car, his body work is yellow and he's sold with a racing car vehicle. Coincidence ? Articulation is Micromaster standard: turning shoulders plus bending but joined hips & knees.
Circuit also forms one of Sixturbo's arms: From his vehicle mode Circuit's back half folds up 90 degrees, pivoting round their rear axles. Circuit then has a fist pegged underneath the front of the vehicle - traditionally the left fist. Circuit is the only one of the four limbs in this set that can't be used to form the other limb type - the peg hole under his nose is mounted too far back to allow it to plug into the peg on the knee of the waist & leg section.
Pretty typical Micromaster car, but with the added side referance to the Action Master.
Circuit was available in 1992 in Japan in the Operation Combination TF-03: Sixturbo giftset.
Streetwise ???? No Streetwise is the Protectorbot Police Car (oddly renamed Prowl in this set) I have no idea why they've used this name for this toy ! If they wanted a G1 name how about Mirage ? Or Breakdown after the Stunticon racing car ? Or even exploited the link above and called him Circuit !
Streetwise was sold as a KB Toys exclusive in the USA and was available in Toys R Us in the UK.