I just bought some Mac mid-length headers which should arrive sometime today via FedEx and I was wondering....do I need o2 extensions with th emid-length headers? some have told me yes and others say no.

 

I did not need them

 

i didnt need them either

 

awesome..thats what I was thinking....how did they fit...any suggestions when installing them? both go in from the bottom?

 

i couldnt get them in from the bottom on my macs. i took off the valve covers and slid them in from the top. it was tight on the drivers side and i used a mallet to get them past the column without any ill effects

 

was there any power difference with em?

 

Mine went in from the top. I seemed to remember the driver side going in with out a problem but I had to take the off EGR valve and coil rail on the pass side.

I haven't dynoed the Formula but my last LS1 car got 50rwhp and 40ft tq untuned. That was going from bone stock to Mac headers and a lid.

 

I put them in from the bottom, took both coil packs off. Did have to remove the oil filter and grind down the infamous block that sticks out. Other than that no problems other than the egr/air stuff. No extensions needed just undo where the O2s are hooked into for movement issues. Picked up 15-20hp at the wheels.

 

I didn't need the O2 extensions either.

Mine went in from the bottom with the block grindage ad mentioned above and only picked up around 15 hp.
The only way I could see picking up 50 whp from Macs and a lid is if the cats were clogged or you are comparing a pull on a mustang dyno to a dynojet.

 

mine went from around 300whp to 330whp on my 98. i liked mine

 

With similar air and on the same dyno?

I could see getting 20 hp plus an extra 10 if you went !cats compared to stock

 

I have no idea if the stocks cats were clogged but when it was stock it ran great so I doubt. The car was dyno'd on the same dyno, I don't remember what the air was like but the dyno is in a climate controlled shop. Believe it or not, I don't really care but those were the results I got.