I have my exhaust ready to go except for one thing, the downpipe. I was under the impression that adding a thermal coating to your header and downpipe would help with exhaust scavenging helping the turbo spool faster. However, there have been a few people that I've talked to that thought I was nuts and the only reason for thermal coating was to cut down on heat soak. I am planning on sending my downpipe to Jet Hot to get their 2000 coating. However, I just wanted to make sure I wasn't wasting my money. Am I right or am I nuts?

Coating the downpipe will help keep underbonnet temps down a little.

But if you're serious, lag the pipes.

I've coated a few pieces so they stay pretty and don't rust.

Thats about it.

Yah, it will help with underhood temps. How much it matters really depends on how your system is configured, and what kind of underhood airflow you have.

I personally haven't really seen many people thermal coat the downpipe, but i have seen plenty of them coat the exhaust housing on the turbo to retain heat and coat the compressor side so that it dissipates heat more readily. I think the main concern with the exhaust coating on the dp is the underhood temps like was previously mentioned....

The only information I can find about thermal coating the downpipe says that it only helps keep the heat out of the engine bay through thermal heat transfer. Which in essence is a good thing.

For the downpipe I would recommend heat shield that stops heat radiation. Anything more isn't really needed.

Exhaust manifolds can be coated, they will reduce the heat loss on the way to the turbine, but not that much.

If you want to coat make sure that you get a real coating, like a plasma sprayed zirconia coating, the type of coating used in jet engines. Not that paint like shit several small companies sell. But note that zirconia is brittle.

Zirconia has a very low rate of heat transfer, that's why it's used in thermal barriers. It should not be used to reflect heat. If you want to reflect heat you want a heat shield. This may be a simple sheet of steel to the more fancy shields of inconel foil or gold coated kapton foil as found in racing cars and space crafts.

Insulation is sometimes used on racing cars and racing turbochargers. They tend to use some carbon fibre based insulation (or similar) covered up with metal foil rather than coatings though.