The motor should be fine at 100000 miles, there are many decently mod'd DSM's running around with over 140000 miles on the stock engine.

Now if you go throwing say a 20G plus size turbo on a somewhat tired high mileage dsm engine running say 24+ psi of boost you will more than likely break some piston ring lands fairly quick.

Another thing with high mileage dsm engines are the valve guides, they are getting pretty loose at over 100000 miles and will cause some oil consumption & oil smoke, just normal wear and tear for the mileage.