Make sure the AYC fuse is in 1st off, on test drive give it some flicking (hard) left and right and listen for any noises from the rear AYC clutch pack (rear diff area) Take it on a longish drive too as sometimes if there's an AYC fault the light wont come on unless you've driven it a way or it's reasonably warm outside.

May sound tappety (unless new 3mm lash adjusters have been fitted) These are easily sorted though for circa £60 from the USA for a set and easy DIY fit.

Check mods have been done to cover any exhaust mods, ie if it's had de-cat system and air filter it may fuel cut in cold weather, so may need ralliart ecu or ecutek reflash to cope.

Listen for noise from top mounts.

Synchros.