I found out the hard way after the Crawford header install, 12 hours of ball, bolt busting fun.
I felt the 4800 feet above sea level (Utah) was killing any gains the headers added. Funny" it only took 8 hours to get them off. (I still have the scares on my arms to prove it) Very disappointed with the low end,drivability the headers produced. I agree a plug change is in order here with a header install.
My thinking is the cam timing is just killing the gains that could be normally had.
Just by retarding the exhaust timing by 2 degrees would get the exhausts ports flowing better and would move your peak power up a few hundred rpm's. The factory cams aren't bad at all, they are just degreed in to hold the exhaust gases in to be re burned. (smog stuff) I went with an intake retard 1.5 degrees and 2.5 degrees retard exhaust. Surprising" I lost no low end torque, plus drivability is great. Maybe a dyno down in Southern California is in order at Church Automotive. Sad" that such craftsmanship engineered headers didn't get the results on my rev-up.
Dennis

 

Would just changing the plugs help my AFR? If so, how?

 

Unless your old plugs were on their last legs, you're not likely to see any noticeable changes with your AFR.

 

with those mods, a tune or reflash is definate.

 

oh yes long overdue.

 

who says they're the best? just because they're the most expensive........

Anyways, I have kinetix cats, MD 1/2'' spacer, topspeed headers (and a bunch of other junk) - did the headers+cats together and got solid gains across the *entire* powerband, no losses anywhere. Oh, but wait, topspeed is chinese junk supposedly so I should loose power across the entire band because I didn't pay $1000 for my headers and didn't need to have the engine pulled on the install

 

It's an overwhelming "opinion" within the posts, try reading them