It might not be the spammy links in the 301.
The only way to tell is to undo the 301
and see what happens to the old re-directed domain.
I had the same problem I had and old domain with 1000 of old spammy links that re-directed to my main domain, after my site was hit in penguin 2.0 I removed the re-direct.
My old domain with all the spammy links is ranking all over 1st and 2nd page. I thinks that google spammy links is just a farce.
I see 2 of my competitor have 70% of there links spammy. Their is more to it then that. I think its just the opposite, to many good links that are
dubious will trip the algorithm or 2 many good links from the same c-class will do it also.