I have an 05 suburban with lack of power in the lower end of rpm. I originally got the code " catalytic efficiency below threshold. So i went to the muffler shop. They said the cats are fine after they did a pressure test of them. we then went further to attempt to find the problem. After some diagnosis, they stated the TPS was bad because it read 20% at idle. After a new sensor and wiring harness, that issue continued. They then said the throttle body itself might be bad. After they tested that, it passed. 2 more TPS sensors, and a check of the APP sensor, we still have the lack of power problem. The truck starts fine and runs smooth, although sluggishly. In addition to this issue, it developed a " noise" in the engine area after a rear main seal oil leak replacement immediately prior to the lack of power issue. We had the transmission separated from the engine and the sound still happened. The mechanic that did the rear main seal went back and checked all his work to the point of pulling the trans again to check that no bolts had come loose. Everything was fine with that work. The sound acts like something loose rolling around in the same location. It is constant in location but not in intensity. It increases with rpm but not like a valve or rocker coming undone. The mechanics who have looked at this truck stated possibly the reluctor ring on the crank has come loose as a problem. They said it could come loose and not throw any trouble codes. My questions are; Does this sound right? If not, what do you think? If so, how hard is it to replace that ring? My K5 is serving as daily driver until i can get this baby back on her feet. PLEASE HELP ME!!!!!!!!