There were some 'dyno tests' done on 400+/- (CID) V-8 engines using the "H/X pipe" in the mid 70s and these indicated some (very small) increases @ high RPM.
However; NONE of this data is relevant to the inline six today, operating on the street.
This engine fires front-back in the header system and different than ANY V-type engine.
This bogus "crossover/ballance tube" was/is used by Muffler Shops to reduce noise W/O changing the mufflers.
Headers WILL make noise; so you must use the proper mufflers and operate it accordingly.
Don't 'fall for' the "crossover scam"!!
Happy trails.
PS: You'll need ones longer than 18".
