Flashing Check Engine Light

Hello, i got a '01 p71 with 85000 miles. It runs very well but when it gets around 65-75 mph it slows down and the check engine light flashes. I changed the MAF and also the plugs.Help me please :)

count how many times it flashes and then go online and see if there is a site to decode the number of times it flashs or hook up a scanner

a flashing cel on an obd-2 vehicle indicates a misfire. Only on obd1 vehicles does the cel flash.