Hey There, I have an 89 cougar super coupe and it is sick. I have been chasing this problem for several years of and on. My car sits under a cover 90 percent of the time and is my on going project. I have replaced the front suspension every part of the brake system, most of the hoses under the hood including power steering and ac,the igy mod and all sensors except knock. I have performed the 20 or so tests involved in diagnosing the pressure switch on the side of the abs unit. When we had the dash out I replaced the evaporator core and heater core. I have also installed headers and built the system to the back with magnaflow and flowmaster parts. and it sounds awesome. but for the life of me I cant get any more than 15 lbs vac at idle,and i have a miss or something when ya get on it. I have pulled codes and performed all the tests. first it was code 49 spout wire prob. pulled harness tested everything u could imagine at least 3 times ran tests at computer harness as well all checks good. Then i got codes saying knock sensor on a friends scanner.took it home and located sensor marked balancer so u could see timing marks and started testing again.. everything passes and timing was right on spec all thru the tests.. take it out and jump on it and she falls on her face...miss miss miss....should mention new belden wires and autolite xp plugs as well less than 1000 miles on most of it. Any ideas? Hope someone out there has been there done that and can help out.