My'04 TrailBlazer (4.2L  6 cylinder, A/T, 165K miles) has recently started to stumble when warmed up fully, and occasionally dies at a stop. A little backround, I bought it with a miss, I replaced the coils, problem solved, ran beautifully, then a couple months later, it started to go into limp mode after about 5-6 miles, this would happen a few times on my 40 mile commute. I had the OBII codes read (CEL was on, and my reader won't work with this car for some reason) , was told the throttle body was bad, it was cold I would have to work outside, so I bought a new Chinese TB, swapped it, and it ran beautifully again, until recently. Now it stumbles when warm, threatens to die, and sometimes does when stopped, turn off, and restart, and it runs great for 5-10 miles. Forums say dirty TB, it only has about 2000 miles on it, I checked it, it looked clean, but I cleaned it anyway, the problem persists. As a test I thoroughly cleaned the original TB, swapped it, but it still has the same problem, no CEL, has not gone into limp mode......yet. What next?