Spoon tb is a 70-64mm..

Is this the biggest an Itr tb can be bored/tapered to?

I had my old itr tb 70-64mm, but was wondering if it could go any bigger
such as 70-65/66mm? Anyone have any experience with doing this?

Also, any significant gains with this kind of modification? Say 11.2cr and aftermarket cams?

Thanks

 

stock is 66-62mm. spoon is 70-62
you can take a stock TB out to about 70-68
You may or may not see gains by doing this, it really depends on the rest of
your setup. I would spend your money elsewhere though, and do this later.