Believe it or not, there are a lot of posers out there, even in expensive Mercedes.
I have personally seen someone with an E550 remove the "0" so it said E55 and had the AMG badge on the car as well.
With the AMG wheels, it would be hard for many to tell the difference.
The dual exhaust out the back and V8 Kompressor badges on the side help, but even then the V8 Kompressor badges can be bought.
Put it too you this way too.
An E550 itself is fast enough to out run a Stage 1 09-10 WRX from a roll. Heck I'd be surprised if a Stage 2 09-10 WRX could keep with a E550 on a 40-120 roll.
The E55 is significantly faster than that.
I ran an stock E55 AMG in my tune only 335i which would trap in the 113+ mph range.
We did like 3 runs they were all quite short from like 40-100 mph and I stayed right with him for most of it, but it seemed as we were approaching the 90-100 mph range he started to creep away.
I have a Stage 1 09 WRX and there is no way in heck I could stay anywhere close to a stock E55 now.
If you are really heavily modded then you may have ran an E55. But if you are moderately modded, you probably ran an E550 with AMG badges
If you are lightly modded, you probably ran an E350 with a AMG badges and a poseur who removed the 3 and the 0 and added another 5.