First off I have a 1991 305 tpi. I want to port my plenum, or get a ported one, and I have some questions.

If I stick with stock runners, is it worth it to port the runner openings on the plenum?

I see some people have ported to accept slp runners, by taking out the material in the middles of the runner openings. If I do this, and use the stock runners, will there be any negative effects?

If I can get one that's ported for a 58mm TB, and use the stock 52mm, will there be any negative effects?

Thanks.

 

The more material that you get out of the way the better off you are also making the outer edges smooth on the inside is just as important.

The only problem you dont want to have is grinding out side the gasket area to a point to where you cant get your intake or runners to seal.. More air flowing happily through your intake will have a positive effect.