One source for car tools:
http://www.zdmak.com/
I would not use a wire brush, there is the possibility that bristles will come off in the precombustion chamber. The reamer just fits and has enough clearance to be a safe tool for this purpose.
DDH

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body. '87 300D w/ Sportline suspension. No more '79 300TD w/ 617.952 engine at 367,750, it was my annual driver to Texas and I sure don't miss it poor A/C heater system!