They say this because the gear drive will create alot of noise which might possibly affect the knock sensor. If the knock sensor picks up this noise (which will actually be a certain range of harmonics) then it might possibly retard the timing because it thinks its sensing detonation when its actually not. I personally think people always say this because the possibility is there and they want to cover their butts incase it did happen and nobody knows what to do or whats going on. Of all the people I've heard this from, not one person has been able to prove it to me yet. Our cars use ESC/EST which means the timing is electronically controlled by the computer (ECM). The ECM will take input from the knock sensor and then depending on whats programmed in the PROM it'll do something. So this means two things, first we can use a scantool to see the knock counts the ECM is receiving in real time, and secondly we have the ability to modify the PROM to act differently when it senses knock. You could program the PROM to retard less timing if the knock sensor did get false knock, some even disable the knock sensor alltogether at certain parts of the powerband, generally at WOT since detonation will most likely happen at cruising speeds or under load (like up a hill). Also, you have the option of changing the knock sensor to one that senses a different range of harmonics. I think with these three things combined, there is a very good possibility you will be able to run even the noisiest gear drive with the TPI setup and be OK. It might not be a bolt on deal with no worries, but there are ways to solve any problems that might come up. There are a few guys on these boards that run the Pete Jackson "quiet" gear drive on TPI w/ the stock PROM and stock knock sensor and no issues at all. But so far nobody has stepped up and said the "noisy" ones work too. I happen to have a Pete Jackson "noisy" gear drive I planned to use on a carb'd motor and I've decided to use it on my next engine build (EFI gen 1 SBC). I also have a scantool and the tools to count knock and modify the PROM. So I'm gonna be doing a comparison between my current engine w/ regular chain and my next engine w/ the gear drive. The EFI system and knock sensor will be the same for both setups so it should be a viable test as far as comparing knock counts. But this will be a while so I dont have any answers on that right now. If you want to do this ASAP I say go with the Pete Jackson "quiet" one since alot of people are running this already with TPI and no issues at all. Check out this thread for more info ...
http://thirdgen.org/techbb2/showthre...gear+drive+TPI
