As a matter of fact I did change both of them thinking that maybe the new front one was confusing the old back one--still didn't work. I asked the dealer to not just read the codes and tell me what they were because I had already done that, so what does he do? He comes out and tells me what the codes were! I was thinking what you were- check the resistance, etc. and see if they were functioning properly but they just wanted to throw more parts at it at my expense. I had tightened my wastegate and found that backing off on that helped the light stay off a little longer but the codes are still triggered within about a 9 mile trip from work. I have no idea why new sensors would change "slow response" codes to "missing or faulty". My turbo also seems to "surge" under full throttle (maybe somehow related?). Maybe an ASE cert. indie mechanic (who isn't flat rate) would be willing to read sensor output. If you get any good info my e-mail is dcgoodwin70@hotmail.com.

Doug