Rep Power: 0

It's really strange but the car will start up and run perfect for the first run of the day. The longer I drive it the more it will get hot and become sluggish when at low rpms. Again it starts off perfect, but will just continue to get hotter and more and more sluggish. Have checked all the usual signs for a head gasket problem and couldn't find anything that suggested it is bad other than performance.

 
Rep Power: 210

How hot is hot? Does the dash gauge ever hit full hot?

Most obvious sign of head gasket breach for this engine is no external leak + loss of coolant in radiator with excess/gain of coolant in reservoir. Check both the radiator and reservoir everyday for a week. Do a radiator/coolant system pressure test while engine is cold to rule out an external leak. Check heater hose under distributor for leak. Another cheap test for blown head gasket is a Block Test (Google search). Does it idle rough or lumpy on cold start or have white smoke emmiting from exhaust? = coolant leaking into one or more cylinders through head gasket breach.
A dry adn wet compression test can also help diagnose a possible head gasket breach.


Othe possibilities for overheat are:
Thermostat
Weak or failed water pump
Radiator fan not working
Clogged radiator

Trey?:

 
Rep Power: 0

No bubbles in radiator, no white smoke. Never idles rough or lumpy even when getting hot. I did notice a slight decrease in radiator fluid but this was after changing the thermostat, so I'm thinking it just filled in the small air pockets still left in the system. Never gets fully hot just much hotter than normal temp. Whats also weird about it is that when it gets hot and sluggish it's in stop and go traffic. As soon as i get cruising around 40 or better it cools off and starts performing normal again. Checked radiator fan and it kicks on while idling. I hear it turn on while driving sometimes as well.

 
Rep Power: 210

While the engine is cold, cover the alternator with aluminum foil and use a garden hose + nozzle at medium pressure to spray radiator fins. Use a spray bottle with 50/50 mix of water and dawn dish soap to spray both front and back of radiator core, let is soak a few minutes then rinse off with medium pressure being careful not bend fins. Also, inspect front side of radiator core for obstructions.

May as well spray off condensor core too while you're at it. If cleaning grease, dirt, grime from radiator fins doesn't solve issue then most likely partial internal radiator blockage or weak (but, not failed) waterpump. Easy way to check waterpump is from cold start remove radiator cap, allow engine to warm up to operating temp and at idle watch current flow inside radiator.. at idle should be a fairly slow but noticable one-way flow. Manually and carefully rev engine and watch for increased coolant flow inside radiator. May even want to do this while front of car is on jackstands (highest setting), turn interior heater to max heat with fan off and bleed out any possible air in coolant.
The engine is cooling better while car is moving because more air is flowing through radiator and/or waterpump is spinning faster to increase circulation.

A block test is cheap.. free rental at O' Really's or Autozone...test fluid is $10.. will help rule out a possibly head gasket breach. You should keep monitoring the radiator and reservoir levels for at least a weak. Also, as mentioned previously a compression test would be helpful.

 
Rep Power: 0

I will definitely keep monitoring it. Running to do a block test today. Think I will even do a coolant system flush to see if that helps. I'm still just as confused as to why I'm losing power only sometimes, and not always. Going to keep doing some diagnostics and let you know.

 
Rep Power: 0

So, ran a pressure test and found it was barely losing pressure. There was a pretty significant deposit buildup around several of the hose connections. Especially around the thermostat housing. Cleaned it up and stopped the leak. Overheating seems to have stopped. Also, as for the power loss, I removed the o2 sensor from the catalytic converter and had more power. Put it back in and seemed to lose it again. Don't wanna say how i will remedy this situation but am certain the problem will be solved.

 
Rep Power: 210

Gutted cat
Gutted cat
What are they feeding you?
Gutted cat
Gutted cat
It's not your fault

You didn't list the car's mileage but, one way to prevent a possible overheat situation is to replace all heater and coolant hoses around 100k miles. A bit expensive but, way cheaper than replacing a head gasket. At minimum replace the U-shaped bypass heater hose and the heater hose under the distributor if oil has ever leaked on it from a leaky distributor o-ring.