RPMs jumping and now truck wont start

[Texas-Red]

Well my truck has been having problems with power surges when driving. The rpms will jump from around 1500 up to 2000 for no reason...this is mostly noticed driving at slow speeds in the city, at highway speeds the problem isn't noticeable really. I had a shop run a scan for codes and try to run a data stream for the icp and ipr but the scanner would shut down every time they tried to start a data stream(they tried more than one scanner...they all shut down). The codes that were stored were P0478, P0470, P1211, P0238 and P1670. I think at least one of them was thrown because of my chip.
The truck as of today wont start. If you try to start it before the glow plug light goes out it makes a clicking sound like a truck with weak batteries. Once the light goes out it will turn over no problem, just wont start.
I've replaced the glow plug relay recently and I know it's good. I'm thinking my problem is my ICP or IPR sensor or the HPOP itself. The sensors were replaced at most 30,000 miles ago so idk why one of them would be bad so soon? I'm needing some ideas here guys! I'm a college student on a budget and can't afford to replace stuff till it's fixed. Thanks for any replies in advance

[cowboyupamrka]

I know this is older and i am not sure if you have had any luck but this sounds similar to the problem i was having, replaced the ICP and IPR and sensors and nothing worked. Anyways long story short it was wires that were grounding out. There is a plug above the driver side valve cover that is under the intake hose. follow the wires out of that plug down the side of the engine. mine were rubbing on the valve cover just out of the plug. separated and wrapped the wires up and adjusted the plug so the wires did not contact eh engine anymore and now it runs smooth. Not sure if the early 99 would be similar, but it is worth a try.