Rising and falling throttle at idle.

[Robert Beatty]

89 200TQ thats suddenly started acting slightly odd.  At idle I get a fast 
idle of about 1400 rpm and then once the motor is warmed up, it cycles 
between 1200 and 1600 rpm, cycling about every 2 seconds or so.  I believe 
its a vacuum leak, but I haven't been able to find it yet.  I've checked all 
the connections, looked over the lines and havent seen anything obvious.

Anyone have any experience with this particular leak and remember where it 
was?  If not, how about some ideas on how to find a vacuum leak thats being 
difficult without pulling every single line off the motor and inspecting it?

Thanks,

Rob