2000 1.5L Accent... 68000 mi on car. 2 Codes--P0136 & P0562

Had Quit completely, mechanic said fuel pump-so put in new fuel pump. Then the first mechanic gave up.

Then next mechanic said coil packs, new and car ran for a while. then got P0301=so put new plugs & wires, now get the P0136 & P0562--

this cars starts & idles smooth although it surges. Will rev way up as long as sitting still. Won't get past 2000 rpm when moving though-- also stumbles like it is choked when trying to accelerate, will get up to speed if babied.