Can someone explain why the WRC cars have such small tailpipes? It doesn't look like they are running 3" exhausts or anything. Looks more like 1.5".

Is that some sort of FIA rule or is there some advantage to that?

They're tuned for the type of power they are looking to get. Sometimes more backpressure makes for better low torque, while a higher flowing unit gets more power up on the top end.

Doesn't more backpressure translate to more turbo lag, which in the end means less low end torque?

I was under the impression that bigger is always better when it comes to turbo exhausts.

Before the turbo spools up, you are basically running an N/A engine. Backpressure is needed running N/A.

Well also, smaller piping doesn't necessarily mean more backpressure.

I have seen WRC closely, and yes they do run 3 inch exhaust systems ..... just because their exhaust tail pipes are not fancy doesn't mean that they are smaller.
According to FIA rules, Group N cars are allowed to use what the std. car uses in the case of both the EVO and WRX it is 2.5".
In Group A and WRC they are allowed to use an xtra 0.5" (they can also use smaller)
The same applies to wheels, they are allowed to use up to 2 inches more in Group A, and the same for Group N. That was a big disadvantage the WRX had on its old Group N homologation there were allowed only to run with 16" inch wheels while the EVO used 17", that is one of the reasons why the EVO on Tarmac rallies was unbeatable.

Carlos H.