No - eisiau doesn't need the "yn." There are a few words in Welsh that don't need it, including wedi.
Is dw i yn eisiau acceptable?
Someone replied to you below and forgot to use the reply feature, but to reiterate, nope, you don't use "yn" before "eisiau." There's certain verbs in Welsh (That technically aren't really verbs at all) that don't use it. :)
OK, so this literally means "nor yes, am i wanting pasta", am I right?