The D3 heads I have messed with had the air injection passages but had freeze looking plugs pressed in. You could pop them out if needed. . .

Does the air injection stuff not work? Why remove it?

 

I will reiterate what I have said on this website numerous times. The younger guys always get on here and tell you to put headers on. If you are towing do not put headers on unless you put on the ones designed for motorhomes. Headers improve high rpm performance but kill low rpm torque. Stock exhaust manifolds have been tested numerous times in several performance magazines and have proven to be far superior to headers for low rpm torque.

 

i was leanin on headers as to not have to plug the air injection holes in my manifolds, but maybe looking for an older set of manifolds would be better?

 

Earlier stock manifolds would be a good choice. They work well for low-end torque and stand up a lot better than headers. You can probably find the left side in a bone yard quite reasonably, but might have a hard time finding a decent right hand side. You can get a new right side one quite easily for less than a 100 bucks. I think I would eliminate the air pump if you can get by without it. It is just one more piece of clutter in the way and it does suck a little horsepower to spin it. Remove the smog bumps in the exhaust ports if you are not going to run the air injection system. If you don’t know what the smog bumps are just look into the exhaust ports and you will see this big hump in there with a hole in the center of it. I have heard reports of a 30 % increase in power by removing these “smog bumps.” (Although I have never seen any documented proof of such power increases) Most machine shops have a reamer that they use to remove the smog bumps and it does a much cleaner job than if you tried to do it yourself with an air grinder. My local machine shop removed mine for $35.00 per head. It would probably cost near that to buy the stones to take them out yourself not counting the hours it would take. It would also be an advantage to go to the local speed shop and buy a porting and polishing kit and clean up the exhaust ports. Don’t touch the intakes as they need the dimple finish effect that they come with. These dimples help vaporize the fuel before it enter the combustion chamber and any attempt to polish the intake ports will diminish this effect and affect performance. You can get on line and for a small sum download complete diagrams on the proper way to port and polish the exhaust ports. If nothing else at least go in there and clean the slag out of the exhaust ports and round off some of the square edges. You will be amazed how much slag and debris is stuck to the wall of the exhaust ports that will affect performance. One last thing, if you use the stock manifolds, take the hot air heat shroud off of the right side manifold. It is my own personal experience that that thing traps the heat in the manifold and is the main reason for the destruction of the manifold.