Shine a light up into the open end of the manifold where the exhaust pipe bolts on and watch the valve move. Then block the linkage in whatever position gives the best gas flow. It's been a lot of years since I worked on one of those emission-control engines, so I don't remember which way to move the lever for "open".
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!