Yep I put that stuff over my extractors on my FZJ105R GXL Landcruiser (1FZ-FE auto).
I hand-formed it, used tinsnips, pliers, and some brute stupidity to make it fit and functional...
Booty-fab special...
I learned the hard way...
WEAR GLOVES WITH THIS STUFF!!!
Originally, with my IR temp gun, the surface of the extractors was up around 280 deg C after just driving around town.
I also have a semi-permanent under bonnet temp thermocouple (measured other side of engine bay near my LPG computer, with a digital meter and K-type thermocouple).
Here are some of the measurements I took after forming the heat shield:
Ambient temperature for both tests: ~20 deg, approx 60% RH, in Canberra (according to my cheapass weather monitor thingie)
Test drive a fixed distance at speed limit (total 8.5km to the shops for sausages and beer...
whilst monitoring temps.
Without heatshield:
Extractor Surface (Cyl 6): 280 deg C
Peak LPG ECU Temp: 95 deg C (Fault code logged)
Passenger side engine bay air temp
@ standstill: 100 deg C
@ 100km/hr: 75 deg C
Drivers left side footwell metal surface temp: 35 deg C
With heatshield:
Extractor Surface (Cyl 6): 310 deg C
Heat shield surface (cool side): 110 deg C
Peak LPG ECU Temp: 65 deg C (No fault)
Passenger side engine bay air temp
@ standstill: 80 deg C
@ 100km/hr: 45 deg C
Drivers left side footwell metal surface temp: 50 deg C
Not a real scientifically valid test... but it worked.
So it dropped my under bonnet temperatures by a lot, but it traps the heat in the exhaust so it heats up the headers (which are Pacemaker brand and are already heat-treated) and makes the driver footwell a bit hotter.
Which makes sense because the extractors are pretty much right next to the firewall there anyway.
I like my feet warm anyway, and it's not hot enough to be uncomfortable.
So to sum it up - my under bonnet now is very manageable, whereas before my LPG computer would shut down due to overheating.
Not bad for a $30 mod...
Hope that helps!
Nick