On the highway, you should not have any cooling issues. I'm thinking the lowering and no chin spoiler are killing you there. I'd think you should be seeing around 200 on the highway. Maybe a little higher due to all your mods. But the thing definately should not climb with the AC on when running down the highway.

As for the fans, you should pop the hood and idle it when it's warm (but not hot yet) and observe the fans. They should come on low somewhere around 200 and kick to high somewhere around 210 assuming the tuner set them to some reasonable values.

You don't have a lower temp thermostat, right? The replacement was a stock unit?

I don't know what you did for cleaning the rad but you probably have to pull it and give it a good power washing. You can get a comb like device to straighten the fins if that's the main problem with it. They're used a lot in the A/C industry.

You can use lowering bolts, just crank them higher due to the smaller pad compared to stock ones. They're about $25 from some of the forum vendors.

 

I bought a 2000 vet when it was over 10 years old. It was obvious that alot of maintenance was required an alot was done. Even though the mileage was low, I opted to change the antifreeze & hoses. A recent 200 mile run revealed that it was running too hot. I then changed the thermostat to a 160 deg. It wasn't till I read a thread about bleeding the heads that the running hot issue was resolved. It took 3 bleeds of each head to get all the air out. Thanks for the tip.

 

How do you get the air out of the system?

 

My engine was doing the same thing (2004 CE)... heating up in city traffic over 230 but okay on the expressway. I found that anything over 45 mph would hold at 220, but slower than that, especially city driving at 25 or less, it started climbing. Finally got well over 240 on the other side of town and I pulled into the Chevy dealer. The tech and I quickly checked the fans, and the coolant level, and everything was fine. I suggested the thermostadt but he said it wouldn't be that, and we both agreed that if it was not acting like the water pump had gone out. I took the backroads back home (20 mi) to keep the speed up and temperature down, and then took it to my own dealer. They found that the radiator was all clogged up with dirt and debris. I'm not sure why as I almost never drive on dirt roads and I avoid, like the plague, paper and plastic bags blowing across the road so they don't get sucked up into the raditor. So I guess it just builds up from blowing leaves and stuff over time.

Anyway, it cost me $180 yesterday to have the Chevy dealer clean it out but on the way home doing 45, it was running way less than 220. I'm going to take it for a "city" drive this afternoon but I already can tell that they found the problem. I had noticed it getting hotter and hotter when we were doing parades with the Corvette Club a couple of years ago, and then it slowly got worse in city traffic over the last two years. If this is NOT the problem, I will be back on the forum to dis-confirm this fix.

 

I had this issue recently, and I ended up replacing the radiator. Problem solved. The radiators on these cars just collect so much debris, it's impossible to clean it all out. I have an 02 and it has 91,000 miles on it.