My comments here are going to sound like an insult, but I don't mean it to, so please take it in the spirit it was intended. Also, they're not directed to you specifically, but anyone who might read or post on this thread...
I've found that lots of people playing RB1 or RB2 report they don't have any lag issues, when in reality their receiver may indeed have the problem -- they just haven't noticed it, or encounter it. For one thing, if all you do is play guitar and bass, then you'll never notice the problem I'm talking about.
The only time you'll notice the lag issue is when you do things like play free-style drums -- fills and Big Rock Endings, or the RB2 "freestyle mode". But if you're not paying attention, you may not notice it.
OTOH, your receiver may actually not have any problems with lag. Unfortunately, unless we're sure you know the details of the problem, it's hard to know which is the case.