I have started to notice 3 thins with my 99 sls

1. Is starting sometimes i have to press the gas while turning the key to get it started then other times I dont and its not like have have to hold the pedal down just get it a quick press.

2. During mid-heavy acceleration dont know if this is normal but I tend to hear like crackling and popping ( not to familiar with mechanics of cars) but to me sounds kind of like the pressure is escaping out somewhere like from exhuast or something only does it during mid-heavy acceleration.

3. low knocking during idle very low from engine compartment.

Any suggestions? Thanks in advance!

Any suggestions? Thanks in advance!
A couple of questions for you before suggestions:

1. What's your mileage?

2. Maintenance history. Has it had a tune-up or other work done recently? Ever?

3. Check for computer codes. (Hold down OFF and WARMER buttons for several seconds, wait for dash lights to go out, then write down codes on message center)

4. What grade of gasoline are you using?

Let us know a little more info here and I'm sure someone will be able to get you pointed in the right direction. The symptoms you're describing are not typical of Northstar engines and some kind of repair is likely needed to get it fixed.