Just got a 1988 325 with 134 k and drove it 100 miles and was running well except it idled a little rough at times and after it was driven for 30 min I would hear a buzzing under the car and at the same time if I am heavy on the throttle it felt like it was starving for fuel, also idle emissions were a bit too high too pass. NOW I decided to replace the spark plugs and removed the copper autolite 66 and put in bosch platinum 4037 gapped at 28-30. while all the plugs were out and wires disconnected I did a compression test 1 cyl at a time for 1-2 seconds each. I put the plugs in and it runs very poor with black smoke so i put the old plugs in and still runs very rough.I marked the plug wires and they are installed in correct order. Did I mess something up by doing the compression test ? Thanks for your help.