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That's my Cabby mate, it does help as any air that goes through the intercooler gets forced through the rad instead of get blown out of the gaps around it. If your fans are behind the I.C then you could still seal up around the out side but you would need to use pipe lagging.
I did mine this way as it meant no mods to the bumper or front panel just a spacer bar to move the bottom of the rad back into the bay an inch.
Let us know if it helps if you do it. Would be interested to see other peoples results.
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