Headers
 

What would be best for a 1991 civic dx 4-1 or 4-2-1?

depends what u want..

its like asking should you go for a truck or a car

both have their own advantages.

4-2-1: 2 peice easily installed, generly cheaper, midrange to top end power (more of a street headder)

4-1 : one peice, generally better flow, but the power is more noticable in the topend of the rpm range. More of a serious track headder, thats interested in the extra 1-3hp at 8,000rpm)

Is this a stock motor? d15 id lean more towards a 4-2-1 header, but honestly, ur goign to see little to no gains with that motor.

Dual Point injection doesnt fair well in the performance world.

Now, find a z6 head, get some nice compression numbers, then i woudll slap on a 4-1 header.