Going stage 2 about a month ago went by the book. No issues, no problems, pure joy. I was even surprised to see how good the MPG numbers were. I constantly clocked the average MPG (using AP) at 28-30 highway and 22-24 city. At one point I got as high as 34 mpg.
Lately the weather has gone south with tons of rain and temps in the range of 40-55F. That's when I noticed something weird about how the engine performs. Mainly, it got hungry for fuel. I can literally watch the fuel gauge needle sink slowly as I drive. Last time I checked it with AP it barely pulled off 23 mpg on the highway staying completely out of boost with an average speed of 40 - 60 mph. The idle also got weird, instead of going all the way down to 650 rpm it hovers at about 1000 rpms for about 10 seconds the then slowly creeps down to a regular 650. The engine also sounds rougher, and there's a slightly noticeable drop in power before 1800 rpms. Once it gets past 1800 it seems to be back into a normal stage 2 torque feel. Another weirdo is how much more engine vibrations can be picked up from the pedals (clutch, brake) and the steering wheel. I'm not sure if that's related but I haven't noticed that before. To finish off the list of symptoms it backfires (pops) when letting off the gas, which has not happened before as bad as it is now.
I really don't know what to make out of all this. My wild guess for a quick fix would be to clean the MAF sensor, since I haven't done that in a while and I noticed that the K&N drop-in filter tends to dirty it quicker then the stock insert.
So to recap:
- lower then normal MPG
- slight hesitation below 1800 rpms
- loud exhaust pops
- high 1000 rpm idle for a moment
- excessive engine vibrations felt via pedals and steering wheel
- no boost loss, steady at about 15psi
- all fluids clean and at good levels
- no CEL
- AccessPort stage 2 93 oct map
- turbo back exhaust
- gutted uppipe
- K&N drop-in filter
I cleaned the MAF sensor, replaced the K&N filter with a new paper (FRAM) filter, flushed a stage 2 93 oct HGW map, did the Vishnu trick, and still not better. It just runs like a donkey, it jerks at lower RPMs, seems to be lacking power, it sounds weird, the smooth power band is gone, all together something is messed up. Ohh yeah, in order to reached stage 2 boost (16 psi) I reflashed a real time map from a regular stage 2 to HGW stage 2. This caused the max boost to drop from 15.1 before to 14.5 now.