Okay I don't really know where too start. I started having these at the beginning of last winter, and I'm not sure what'* going on. The first two are related. The engine is running lean. I swapped back to the stock air box at the beginner of the summer, but it is still too lean. I changed all the plugs, wires, and o2 sensor and still, nothing. I think this is causing the engine to knock.
When driving on the highway, if I put any boost on the engine at all, it will start knocking. Like, if I try to pass someone or go up a hill, my engine sounds like a rattle can and there is an obvious lack of power. Im getting readings of around 3 to 8 degrees.

I don't know why it'* running lean. Is it not getting enough fuel, or something else?

As for the coolant temp issue, this one has really got me stumped. Every cold start the engine heats up to around 225* then quickly drops down to around 188*. Then it usually hovers around normal operating temp. Of course the temp can't change that drastically that fast, so could it be a wacky sensor? I had a shop do a pressure test and they found a leaky water pump, so that and the thermostat have been replaced, but there is still a small leak somewhere.

You need to fix the lean issue fast, because it can cost you an engine. Lean means that there is not enough fuel in the mix, so you will want to check for fuel delivery issues and vacuum leaks.

The second concern may simply be an air bubble stuck in the cooling system, or a sticking thermostat.

your fueling is based on your temp so if you have a flakey ect it will effect all those other things. are you missing coolant at all, the other thing that comes to mind is lower intake gaskets. thermostat might be sticky too

How do you know it'* running lean?

Were any codes set?

Is it knocking or misfiring?

Are you losing coolant?

Get a fuel pressure gauge and run it up to your windshield under the hood in such a way that you can see the gauge while driving. You need to see the pressure peak under severe load.

I don't think his 188 temp is causing any issues. These computers are designed to go into closed loop after 160* anyway. My car will do the same thing and I run a 180 t-stat. During cold run, it will gradually warm up to just about 200*, drop down to 180 and stay there the rest of the trip.

Oh, and have you tried cleaning your MAF?

I cleaned my MAF when I put the stock air box back on and I changed the thermostat with the the water pump. As for codes, I haven't got a lean code since I took the the K&N out of the fender, but the two shops I took it to told me it was still running lean. The plugs looked really lean too.

I'm getting up to 8* of knock retard with just a little bit of boost.

I want to check for vacuum leaks, but I'm not sure how to do that.

And Mike, do you know of any way to check fuel pressure with the aeroforce gauge? I'll look at the manual later (if I can find it), but maybe you know?

No, not on a 98 system. Some of the newer luxurious cars have the built in sensors.

the parts stores have free rental for pressure gauges

Okay, I'll have to take it too a shop or rent one soon because it'* only getting worse. I'm now getting a near constant knock around 1-3* driving on the highway. Idk if it was the fuel I put in or what?

As I'm typing this I realize that it'* probably better for me to take it to a shop. Have them check the injectors and look for vacuum leaks... Man, this is really bumming out. : (

what does your fuel trim look like