Hello I have a honda accord 2002 v6 coupe I had my engine run hot due to a busted radiator and lack of antifreeze (that's all I thought it was) and I got a engine replacement but this one also ran hot and like the last one, it was messed up to the point where it would be lucky to touch 1500-2000 rpm or go over 5 mph. So I Iet it sit for a while, and then I realized. The car goes a little faster in reverse than in drive. Also the d4 light on the dash keep blinking, regardless what gear. And also, after letting it sit, it was touching 2500-3000 rpm. And it wasn't running hot anymore and it was driving close to 30 mph if I didnt brake. So somehow I got the wild idea that maybe my catalytic converter was bad. So I cut a hole in the front exhaust and then drove it. It was very loud and it also was moving fast as ever. Other than the d4 light blinking and the power steering pump being broken, everything seem fine. What do you guys think? Install a whole new exhaust system and the car will be good? Could I maybe throw in a cold air intake with a turbocharger and I ktuner v2? What are my dos and don't in this situation?

 

Your car came from the factory with a cold air intake, all an aftermarket unit will do is make the engine louder. As for turbocharging, it will cost you more than the car is worth; that plus the fact your car has an automatic transmission well known to be extremely fragile means a higher output engine will cause repetitive transmission failures.

Long story short, if you have that much money burning a hole in your pocket, sell your car and buy something designed to be faster from the factory; it will cost you less and be FAR more reliable.