5vzfe "rattling" while cold and under load

Hi, I have been having engine issues on my 97' 4x4. When cold and accelerating I experience a rattling noise that sounds like it is coming from inside the engine. The colder the truck is, the more prominent the noise (the ambient temperature seems to have an affect on the problem). Even when the water temp has leveled out the noise is still present for the first few miles of driving. The noise becomes much less prominent after that period, but is still present, and sounds more "normal".

The worst experience with the problem was driving after only a minute warmup. When accelerating the whole truck would shudder violently. The shuddering got worse when i applied more throttle. The motor warmed up out of the issue and the check engine light did NOT come on. This has only happened once, as i let the truck warm up fully before driving now. Any help with the issue would be much appreciated.

*I have replaced the spark plugs and wiring(by the book spec plugs/tq values). This did not fix the issue.