spec ops is always ****ed up for me. whenever i go on it it just lags like shit. and before someone says it, its not my connection because i do not host and both players lag.
ive been helping people too and if u get too many people, ill help anyone out and the spec op trophies. that pain in the ass one; kill 3 people when your down. ive experienced terrible lags too from a few people too. both connections have to be fine for it not to lag.
to get the "kill 4 enemies while downed" achievement, I just started a split screen game at the burger town one. Left one guy at the start, Downed myself behind some cover and shot 4 guys...really wasn't that difficult.