Hey guys,

My m20 and m52 engines feel silky smooth, but the m50tu is getting a little rough. But what is bothersome is that the idle is pretty smooth, it just feels like every now and then it gets a little lumpy - not too big of a deal. Cruising / highway cruising is also smooth as can be, however acceleration is a little bit rougher (to be expected) - but high rpm (4k and above) feels like an old, tired 4 cylinder - it just sounds like its straining and it vibrates very strong. My m20 and m52 are just silky smooth above 4k rpm and if I give it gas, they pull nicely... not this one. It's annoying when I want to pass on the highway and it just vibrates.

Any ideas as to what this could be?