Hesitation under full throttle
 

I'm new to Mercedes cars. Ive got a 1999 SL500 that was parked for 4 years. I've been going through it and have replaced the fuel filter and crankshaft position sensor. It has new gas in it. The idle is smooth, and half throttle if smooth. However, put your foot in it and there is stalling and hesitation. Any ideas as to what's causing this?

Stalling
 

The first thing that I would check/replace are the plugs. I paid the big bucks and put in the Beru suggested ones and they do work very well. Have you checked the air filters? Try removing them for a mile or two to see if that helps. It also could be just carboned up so find a place where you can WOT
for about ten starts at WOT. If you aren't getting engine light problems then its probably just lack of use. A large can of Techron helps a great deal also for cleaning out the engine not to mention increasing the power. If none of these help then give us an update and more info can be provided.

Thanks for the suggestion. I haven't changed the plugs, but probably needs it. The PO wasn't too good with maintenance. The air filters are new. I've cleaned the MAF Sensor, and will replace it soon as they are consumable. Engine codes showing are P1070 and P1073. I've tried blowing it out at WOT, and will continue to do that just because its fun.