Are T.O.G. headers any better or easier to install than SLP headers? Does either one need to go to an aftermarket cat or downpipe. I would like to use the best kit performance wise even if it means replacing the OEM cat. Is it possible to retain the stock cat with either of these kits? Any advice greatly appreciated!

howdey, The only opnion I could give would be the cat. I would be suprised if an OEM cat is as freeflowing as an aftermarket cat.
With headers IMO if you are spending the $$/ time to buy and install, it would only cost a few bones more to get aftermarket cat, muffler, o2 sensor and the pipe work for the rest of the exhaust.
It would take a $700 headers and bump the price up to en even grand for the complete package.

pricy upgrade..but atleast the exahust will be at a top performer.

whatever you do decide, get jethot or ceramic coating. it looks great and it keeps the underhood temp cooler. Ive done it on 2 cars and swear by it.

goodluck
cheers
chad

The SLP headers have not been out long enough to get enough information about them IMO. The TOG headers have been out a while and are proven, but they cost more money. Neither headers need a different cat or downpipe, but I would highly recommend one. The TOG headers are supposed to have larger pipes than the SLPs, but that may not necessarily be a good thing, depending on your mods. I don't think either header is more difficult to install than the other, it basically is just which one you like better. I definately recommend getting a ceramic coating on them though, because it will drastically reduce underhood temps. We have Ceramic Coated TOG'* on our GTP and they look & perform very great. IMO the TOG'* are better just because I have personally seen both in person and the SLP headers have sharper bends in them, and have smaller diameter pipes.

Thanks for all the info but I have another question. Once I install the headers will it be possible to change from a high flow cat for example to an off road pipe to compair the difference of the two without too much trouble, meaning not having to go to a shop for cutting or welding together.I would like to try different down pipes but leave the headers alone.

I am pretty sure you will have to cut and weld. I think you can buy both the SLP & TOG'* with downpipes that just bolt right on, but you have to use that one particular downpipe, so you cant switch to a different one without welding, I don't think. If you go to 3800performance.com I believe they have all of the bolt up downpipes on there so you can look at them.