this is why the type r has done so well. that and the fact it is indeed a good platform. but the ability to pull things off the shelf to tune isn't all that bad. but using itr in the speed touring car championships is kinda too easy. it would be like a g20 guy saying, well the primera kicked ass for 5 years in the btcc. the lack of an aftermarket, or abundance of one has very little to do with the quality of the engine, but moreso the demand for products. a better example in the speed touring car championships would be real time's rsx. it did nothing, because it has such a small aftermarket.
anyways, the silvia (s13) at least, should make less power to the wheels than an itr stock for stock, just because of rwd and the weight of its running gear, but it doesnt make the silvia less potent.