Another New C6, S6 owner with a couple of questions as well

Hi, my name is Dennis and recently ( about 3 months ago ) I decided to give up on the old Cadillacs and grab one of these bad boys for fun. It is a 2010, Pearl Black with only 87000 miles on her. I knew I would have to spend a bit of money to make her my own and get it running perfect and I am almost there but I have two different issues that I am kind of stumped on.

The first is I get a trouble code 00135 ( Low Pressure Fuel rail/system ). It seems to pop up if I am in Drive mode only and I decide to accelerate more then normal. What that means is, if I baby the throttle, I get no EPC or Service Engine Light. If I give her half throttle off the line or make the beast drop a gear while in motion it pops up. If I use manual or Sport mode, never does it pop up. This took me awhile to figure out but it is true, I have tried to get the car to flash me the EPC light or service engine light in both of these modes for over two weeks with no luck. I did replace the low pressure switch to verify I was getting a true reading and at first after replacing the switch ( for about the first 200 miles, no code, then it decided to happen again ).

The second gremlin I have might be associated with the first one but who knows. Every once in awhile ( seems to be when tank has just been filled to the rim ) it stumbles on start up. Now, somewhere I heard that I should try the following method to see if I get the same problem. Turn the key to ON, press the gas peddle half way and let go, then turn to start. Since doing that, starts every time perfectly ( no long turn overs either ) which I noticed a few times especially when warm. Now I have not gone back to normal starting since but I wanted to make sure that I kept to the same routine until I fill up the tank again and see if the gremlin comes back. You know, process of elimination. Owe, I get no codes for the stumble at all, just happens and it seems like as soon as it gets enough fuel to the engine, she stops stumbling and runs beautifully.

I have already replaced the fuel filter, it has had the good old carbon clean, new coils, new plugs, new SAI etc. All in all, the car runs really nice except these two issues. Would be great if someone has had similar problems and insight.

When I got the car, I brought it to a reputable Audi/Volks/Porshe and had them do a nice scan of the vehicle and we had noticed that the TPMS was disabled in the car which told me that whoever ( one owner ) had the car, had someone that was able to modify the parameters in the computer probably using VCDS. Now I have recently purchased a legit Ross-Tech connector and I am going to use it, but want to read just a little more on how all the channels / adaptations work, can really screw something up if you don’t know what your doing right. I am thinking that maybe this individual messed with something else and thus the reason for the first problem I mentioned or both…

Thanx for hearing me out folks, I have learned a lot in the past few months just reading everything you guys right in here, it’s awesome…Thanx D