wierd idle

[6.0bigred]

I have a1999 Silverado 2500 4x4 6.0 that I just got running again it has been sitting for 2 years because my girls dad was going through some rough time and didn't really care now 2 years later he is in no shape to be under a hood or on his back messing with the thing anyways I needed a vehicle and he said if I could get it running I could use it I went and bought a can of sea foam a 10gal gas can with gas and battery put everything in/on and it started right up like it was nothing I was like sweet since then witch was 2 days before this post ive don a oil change wit 10w30 Castrol edge high millage and k&n oil filter a much needed bath all new lights toped off dexcool, power steering,  witch is leaking but the whole reason I was making this post was when I stop at nights 2 things happen AND ONLY SOMTIMES the gas peddles feels like its getting stuck when I go to APPLY presser but not on release  and it idles funny but if I put it in natural and rev it the put it back in gear it will idle normal the rest of the time till the light turns green but at the next light it may or may not do it what do you think it could be

[silveradosid]

no idea of mileage but if it isnt constant i would clean the throttle body first and mass  air flow sensor

[Logan Lanfear]

Also this is the wrong forum for this.  Thats a new style GMT-800 truck.