'slip' light came up after putting new wheels

Your tire sensors are sensing different size tires./ Your tires are rotating at different speeds because of the size difference. put the same tires on the front axle if front wheel drive. and the same tires on the rear if rear wheel drive. be sure to match tire pressure.

in response to your ESP and slip question above -- check your wheel bearings. I had this problem recently. Both my front wheel bearings were loose

check operation of vacuum diaphragm under battery that actuates 4WD cable

I would have the computer checked for trouble codes first.
If the hydraulic part of the ABS is faulty, it will apply pressure to a wheel even if you don't need it.
It measures wheel speed to see when a wheel is spinning or slipping and applies brake pressure to that wheel or the other three.
Or prevents you from applying the brakes.

Some tire pressure monitoring systems don't care if the wheels were put back on in the same position they were in originally.Unfortunately I think Subaru's do.If the light hasn't turned within a few miles of driving you will need to have your monitoring system reset.Most tire shops have the needed scanners but if they don't,do you Have a Discount Tire in your area? The last I heard they do this for free.Good Luck!

are they chrome inserts or plated cutouts with plated chrome on them ..sounds like a ting -ting noise or light tapping ...or are the rims solid if my first question was a yes then try see if they are all secure and not loose this has to many different style of rims or is it an internal sound other than the tire issue ...such as wheel bearings or possibly the brake guard rubbing or loose ?

check the cable which leads from the tranny to the dash, most of the time the cable or sensor went bad

you have a computer for your control on your car. It is set up so only the factory front and rear tires sizes will work, any change, it picks it up. this should solve the problem.

different tires, same rims.

TCS is Traction Control System,and all TCS's are controlled though the Anti Lock Braking (ABS) system.Here's how it works:Each wheel,or in some cases,only the drive wheels have a speed sensor mounted near the hub or axle,and sends a speed signal to the PCM (Powertrain Control Module).The PCM monitors wheel speed continuously,and if it sees a speed out of the ordinary,say for example the right rear tire is spinning and traveling at a much higher speed than the left rear,the PCM will pulse the brakes through the ABS system on the right rear to slow down the right rear so that the left and right wheel speeds match up,this is how the traction control works.So,if you have a TCS problem,the PCM will see this and set a Dignostic Trouble Code (DTC).You need to pull the DTC's out of the system with a scan tool,diagnose and repair the DTC's.It could likely be something as simple as a malfunctioning wheel speed sensor,but you won't know until the codes are pulled out,as this will point in the general direction.Good luck.