don't do it!! leave them be. my sled had a bad low end lean bog! ran like crap. I don't understand this, people say to do this so the valves open sooner so the motor revs faster, but the stock springs are to light, so they put a stiffer spring in to compensate. whats the difference?? whats the point??
I strongly suspect your sled is lean to begin with,(or other issues?) and by the valves opening sooner, it just becomes more noticeable, that's all.
Tuned properly, whether it's richening it up via the fuel controller, or a different exhaust spring combo, real life results have proven the plugged valved sleds to be quicker.
On my 2007 D7, I plugged them and left the stock exhaust springs in, definitely noticeably quicker in acceleration compared to my bud's identical D7 test mule sled.
Remember Casey's 160+ h.p. D-8 dynoed at Dynotech? When I asked him about plugging the exhaust valves, he said he already runs 'em that way. That should tell you something.
The overwhelming majority of the feedback I've rec'd is it works!
It's either that or actually I just post up this B.S. so that Monte can sell more of his soon-to-be-patented exhaust valve plug kits (which I'm a silent partner in that business) and we meet every year at the hide-out (Rustic old restaurant in the Northwoods called Little Bohemia the Restaurant where the Feds almost caught John Dillinger and accidentally shot some innocent civilians by mistake) Monte brings a duffel bag loaded with cash the end of the season and we split the profits.
ound: 
