lil more problems

Ok sumtimes my car idles fine then itll drop to 1 then under 1 then go to normal again, also when i try to go and press the gas, it sounds clogged and i dont get going until it sounds like it clears up at around 4000rpm, and then same wit 2nd gear but not wit the other gears, so outta first gear up to about 4 it sounds clogged and wont accelerate as quik as normally, i repeated myself...