I've looked through several threads on this header and it seems like everyone is getting gains of at least 10hp. I know it may not be the best header, but I think it's the best for the money. But it seems like everyone else has at least an aftermarket downpipe with it. Am I going to get this significant hp gain with an otherwise stock exhaust?

The only other mod is a ZZP 3" CAI.

 

I doubt you'll see much difference to be honest. Sound might be a little deeper/throaty. I might be wrong but a 2.5 catless DP is only like $150 from ZZP or OTT.

I went BadMab Shorty and ZZP 3" Catted DP and stock CB. Much better sound. I just don't want to go any louder so am holding off on the CB.

 

OP, don't waste your time with a 2.5" downpipe on the LSJ. If you are going to purchase a high flow downpipe get a 3". The Badmab's collector is 3", and if you want to obtain the best flow combine it with an equally matched 3" downpipe. Also, it is one of the best headers for this car. It actually has proven gains vs. all the talk about longer tube headers being better.

If you just bolt the Badmab header on your car, and run it with the stock downpipe, you wont notice much of a difference, because you are exiting exhaust gases out of a 3" collector into a smaller opening. The inlet of the production downpipe at the flex coupler is only a pinch over 2". It then opens up to 2.75", but that small inlet will pose as a restriction.

I run the Badmab header into a 3"-2.75" catless Random Technology downpipe, and I def felt a nice bump in power through the mid-upper rpm range.

 

So am I better off buying a 3" downpipe before the header? I don't have money for both right now.

 

Yes, you will open up some flow with a 3" downpipe even if you're still running the stock manifold.

 

^^
This. Def go with a 3" down-pipe, otherwise you will be replacing it later when/if you want to do more to the car. However, you definitely should get a down-pipe.

I have a Bad-Mab with a ZZP 3" catless d/p with stock catback. Personally I like how it sounds now. Sure could sound better but nothing I'm worried about until I finish some other small upgrades.

 

And with an intake and downpipe (possibly a header in the future), I will not need a tune. Correct?

 

If you want every little bit of power you should get custom tuned for your mods, but you should be ok with an intake and downpipe as is for a bit. You wont hurt your car if thats the answer youre looking for.

I should warn you though that you will get a check engine light with a high flow downpipe. There are 2 ways to avoid this. Get tuned, or buy an angled 02 sensor bung. You can purchase an angled 02 sensor bung for about $10-$15 on E-bay.

 

^^^do you have a link for the angled bung, i bought a 3" downpipe with the spun metal cat.

 

No, sorry I do not.

I myself have the rear O2 sensor tuned out. I know that modern performance sells them, and if you type in angled O2 sensor bung on E-bay you will be sure to find one.

 

You can typically find them on ebay for pretty cheap (it doesn't need to be anything fancy). Modern Performance has them as well.

 

What about the 3in ZZP downpipe that tapers down to 2.5in. Would that be better performance wise with the badmab header?

 

Yes. The 2.5 tapper is so you can install the 3" downpipe to a 2.5" catback. It will work well.

 

Thats what I did. Just have to buy the catback now. A full 3" exhaust would be nice but it is just too loud for me.

 

Also, a full 3" exhaust is not needed for 90% of the blower cars (SS/SC's) out there.