Anybody know who makes a good quality header with proven results for a 4cyl. Hardbody? Any info provided would be appreciated,

P.S.
I have a 2 1/4 in. exhaust on my truck at the present time. Should I stick to this system or would upgrading to a 2 1/2 in. pipe produce more power without sacrificing too much low end?

Thorley's are excellent if you got the $$$.$$. Thorleys provide a lot of low end torque. Their worth the mula!