1990 GMC Sierra 350 TBI runs rough

I have a 1990 GMC Sierra K2500 w/ 350 TBI w/ 203,00 miles on it. All of a sudden the thing has a engine knock and also runs weak as heck like it is getting no fuel. I used to have a Duramax and I know how it feels when the fuel filter gets dirty and this is similar but the first night it happened the was a suttle smoke coming from behind the Throttle body area that I could not find exactly where it was coming from. I starts up fine but has the power of a 5HP briggs and stratton. Is this a simple fuel filter or regulator problem or something in the motor because I am not sure the knock has anything to do with how weak it is running. Any comments would be welcomed.

Well the engine knock will affect the timing for sure as the ECM will retard the timing.

The smoke behind the TBI also concerns me. It could be coming from the EGR or intake gasket. Maybe TBI gasket. Could the smoke have come from the coil?

Probably need to start with basics: compression check, fuel pressure test. Have the engine scanned to see what the ECM thinks if the engine is running rich or lean.

Any codes stored?

//2000CAYukon

I wanted to check and see if it just had bad fuel or maybe water in the lines so I left it running in the driveway and let it run completly out until it cut off. I then put some 93 octane in it and got it started back up after a few turns and it ran a ton better but just on the low end like 1 gear is weak and the other to gears in the TH 400 tranny was just back to normal pulling power. They knock was still there but I just think it has a piston knocking and eventually will ne tending to. I just put all new plugs in it and not sure about the timing but when it got weak the first time I was on the interstate and it flashed a service engine light for like 3 second and has not come back on sense. I am going to change my inline fuel filter and take to get codes ran and go from there. Thanks for the reply. I am not optimistic that this mechanical sga is over at all!