I would stick with stock ITR springs and retainers as well. As a matter of fact, the retainers may be exactly the same as the b16a units. As long as you don't have plans to upgrade the camshafts later on, you will be fine. The stock ITR valve springs will keep the engine noise down unlike fairly stiff aftermarket valve springs, but will not control a much wilder cam then what you have now. It all really depends on what you plan on doing in the future. Don't expect the stock springs to be cheap either!