The knocking and pinging is back

[Badco]

Ok, if some remember from a month or 2 ago, I was having some issues with knocking and pinging on my truck. Turned out the MAF was bad. It was replaced and life was good. This week, however, the damn thing started to knock again.

I have already unplugged the MAF hoping that it wasn't a problem again, which it isn't. It continued to knock with the MAF unplugged.
O2 sensors (the two on the headers HAVE been replaced about 3 weeks ago). Gas mileage has taken a nose dive. I'm lukcy now if I am getting 260mi to the tank. I was getting close to 300 previously.
It's not smoking or anything. Air filter is clean. It gets regular oil changes and checkups.
It's a '98 w/4.3, auto. 107k mi on the odometer. Mods are the easy DIY stuff (EGR, air, TPS, HTT3, T-stat...etc). No codes being thrown.

I need some help trying to figure this damn thing out.

[Sparky2263]

Ck. fuel pressure.

[Badco]

Ok. I'll give it a check.

[Badco]

Sparky, Chevy dealership says the pressure is good. I wasn't able to get into specifics as I wasn't there to handle it myself.

[Sparky2263]

What else did they say about the knocking?

[Badco]

DO the usual check ups (plugs, wires, MAF, etc.).

I wasn't in town to talk to them face to face. Had to relay everything thru someone else. Probably a mistake to do it that way.