W124 500E Help! Bad Cold Start w/ heavy smell of Gas!!

[danny500e]

***LOT of info here. Tried to go into detail the best I could. Cliffs:

-Car is EXTREMELY difficult to start when cold.
-Strong smell of gasoline after the car has been sitting.
-"Chuggs" when cold, as if missing when sitting idle in gear. Idles fine when in Park while cold.

See more details below:

Hey guys, I did a quick search, but it wasn't extremely helpful.

I've had my 500E for nearly a year now, and I've loved every bit of it.

About 6 months ago, it developed a difficult cold start; taking solid 25-30 seconds of cranking before turning over. This is when the car has been sitting over a period of about 8+ hours. After starting, it would "chug" a little as if it were experiencing a slight miss.. The "chugging" was only experienced while in gear. If placed in Park, the chugging goes away and the car idles normally.

(side note, while the car "chugs" there would be a loud "knocking" noise coming from what appears to be the rear of the car, under the passenger rear seat. Once warm, the "knocking" would disappear.)

After completely warming up (say the end of my commute), it would run perfectly fine.

Now, it takes a couple of attempts of 30 second cranking with a bit of pumping the gas to start. It will backfire quickly before struggling and will weakly start.

There is also a VERY strong smell of gasoline when the car sits. There is a faint smell of gasoline when driving, but I think this may just be the smell lingering since it was so strong while sitting still. I've never experienced the smell until recently, when it became extremely difficult to start when cold.

There is no smoke on start up, even when cold.
The plugs do not look foul. Excessively burnt or carboned up. (Although they do appear to be a bit more "Tan" than usual with a hint of corroded "green?")

There appears to be no leaks, at the FPR, Fuel Rail, or injectors.

Please give me a hand. I love her, and at the moment, shes my daily! Quite embarassing to sit in the parking lot at work and struggle with such a pretty car