You are still wrapping 3x or more the surface area... the wrap reduces the amount of heat loss... but its still 3x what would be lost from wrapped exhaust from Manifold (to the Header collector).. My exhaust is stock 02 Manifolds.. mildly ported... heat coated.. then exhaust wrapped back from the manifold.

Oh... and its on an 408ci motor..

 

Yea i was gonna get them coated and wrap the rest of the exhaust. Who coated/coats your manifolds???

 

What y-pipe are you running?

 

yea use stock manifolds.. i only have the LT's and ORY still on to make my life easier with all the work i had to do/have done