You can't really undo not porting and polishing a head because it's already bolted on. If you tear apart your engine again there's a whole lot of stuff you can do for fairly cheap (porting/polishing stuff, recontouring). The biggest restriction in those vehicles unfortunately is the entire system. 2.3L's have small ports every where even for a 4 cylinder.
As for an insulator are you talking about for heat? If so, you can get those "heat wraps" that are meant to wrap around exhaust manifolds and turbos meant to keep heat in, and instead use it around the intake to keep heat out of the intake.
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2005 Suzuki Hayabusa GSX1300-R
1980 Ford Thunderbird - 255 V8
ported heads, 5.0L ported stock headers, O.R. H-pipe and Flowmaster 2-chambers, dual roller timing chain
hi-po Mack Truck hood emblem 
1985 Mustang GT 5.0L T5, F-303, GT40p, headers, off-road h, flowmasters, MSD stuff, etc.
Sold 02/06/04 
1989 Mustang GT ET: 13.304@102.29 mph (5-24-03)
Sold - 1998 Mustang Cobra coupe, 1/4 mile - street tires: 13.843@103.41 (bone stock)
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