i have an apn header, took about 5 hours total to install. it works nice and i just had to do some minor clearancing with a grinder on the flanges between the intake ports and the header ports. no biggie. have a grinder on hand, have some copper permatex spray and you will be good to go. i used antiseize on the bolts and just check torque each few months. no biggie. all bolts can be reached from the front , remove the PS pump and set it all aside. you can reach all but the farthese back from here.
best of all, have a great time.
apn headers are decent for the price. just make sure the intake and exhaust flanges slide freely between one another before attempting to assemble. i should have done this and made room before it wasted an extra hour. no need to remove the FI rail all you have to do is unplug everything.
if i can do it, anyone can.
a comparison:
removing the intake portion:
old manifold left to remove:
after removal of intake and exhaust:
needed some more room:
a little clearancing on the manifold too:
smooth sailing after that.