[trex]

is it o.k. to run twins on a stock motor or does it need to be ported?

 

[CrossRev]

You can run twins on a stock motor, SLP sells twins and it doesnt say that you must have it ported. It would just have more hp if you ported it.

 

[CHICKENHAWKF7]

you're probably better off running the stock pipe, over twins. The porting and use of the stock pipe will pick you up more than just bolting on the twin pipes.