I've clenaed the intercooler on my 245 once. Just drained it and flushed it with soapy water, seemed to work OK.

As for your second question.. Which is more important to you, being cool in the summer or gaining the maximum horsepower? Seems to me like there's an inverse proprtion to how you value A/C and intercooling. If you value A/C a lot, leave it stock, If you value A/C a little, turn it off when you want maximun boost. If you don't value A/C at all, take the whole works out of the car. Moving the intercooler in front of the condener would make the turbo work better, but the A/C would suffer, so.. where are your priorities?

Bob
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91 740 Ti 173K
82 intercooled turbowagon 237K
67 122 wagon