Just some FYI,
I am in SoCal
I have never used any devise to heat up my intake manifolds.
I have always used headers.
I never had cold starting problems,I actually wanted to make my intake manifolds cooler,it picks up plenty of heat from the headers.
Probably because of where I live the weather does not play a role in needing intake manifold heating.
When set-up for mileage,I was able to get decent mileage of 22-24 MPG w/a small hyd camshaft & a 5 speed manual trans,all done w/out any carb or intake manifold heating.
Just ,my personal experience,others will have different outcome & am sure.
MBHD
