midnight rumbler

I seem to have a slight bogging issue with my '89 350. When at idle, it will sort of surge but not to the point where I can see it on the tach, I can just feel it. When I am at accelleration or highway speeds, I can sort of feel the truck bog down a little and the exhaust stinks like fuel.

I have replaced the fuel filter, changed the cap and rotor, plugs and wires and still have the issues.

I believe my Fuel pressure is adequate as there seems to be a good flow to the injectors and my vacuum at idle is 20. Idle is at 800rpm

The funny thing is there is a little bolt on the side of the TBI unit and if I remove this bolt, the truck is losing vacuum but seems to run better but idles higher. the reason I had done this is because that is where I tapped a vacuum gauge into and by removing the vacuum line, it allowed pressure to be lost but makes the truck run better. If I plug the hole with my finger while exposed, the truck will bog down again.

I recently replaced fuel lines with factory specs and filter and have since replaced the filter with another new one incase the last was faulty but I am still having this bogging issue. I have also cleaned the injectors by removal and added fuel injector cleaner.

Not sure if this is related t the issue but I can also hear a pinging sound but cannot locate the exact source. It seems to be coming from around the TBI unit but I cannot tell for sur. I am using an automotive stethoscope but cannot pin point the exact location of this noise. Sounds like a ping but is not coming from the rockers or the PCV valve

Any ideas would be great