Need Idle Help

Help, Just got a 80 280zx that runs great except Idle. It acts like it has a vacumn leak. Sometimes it backfires in intake and exhaust when cold and Hot. It also has no cold idle. It appears that #1 and#3 cylinder are not firing very good when shorted at idle. Compression is 160 all across and injecters show they are firing by the test light. Timing on and valve clearences. Above 2000 rpms runs okay but may lack a little power. I have done plugs wires and coil, pcv and replaced 1 injecter in #1 cylinder. All sending units appear to be working and exhaust stinks from being too lean I believe. Fuel presure okay. To start cold I have to hold gas down a little. I would appreciate if any one has any ideas or has had this problem. I have a gut feeling it's like a vacumn leak effecting #1 and3 but not positive. Thanks