Header Question
 

I have a gsl se with around 25,000 miles on a factory rebuilt engine. I have installed an RB cat repacement pipe and pre-silencer along with a k&n drop in filter and high-flow muffler. The difference is noticable. I'm considering buying an RB header, but my question is, with the upgrades I've already made, will a header really make a worth while difference. Will it be noticeably quicker, or just noticably louder? Thanks in advance.

A good header should increase horsepower by some 15-20 %, say about 20 bhp. The impact will be up to a second knocked off the 1/4 time and about 5mph increase in top speed. There will be no significant change to noise level.

As a general rule improving the header from stock is the most cost effective modification of all. My view would be yes, unless you have another expensive habit!

However, only you can tell if the improvement justifies the cost depending on your budget and predicted car use.

Get the header. Not only will you see an increase in performance but you'll ditch that damn exhaust manifold. Just looking at it makes me sick (it sits on my garage floor :) ). A header also allows removal of a lot of other stuff, assuming you don't need to pass emissions, and thus cleans up that side of the engine very nicely. With my RB header on my 88 engine, I took off the airpump and now can easily access both port actuators. Very nice since I used to be able to only get to the rear one. Good luck.

Redwood is right. You will be able to remove many other parts when the header is in place and the weight saving will make it worth it. Just make sure that you get the header with the actuator port to open up the sixth ports on our 13B.