just got my block bore to 81.5 do i need to sleeve the block if I'm going to boost going for 400-500hp

 

I'm going to say no. Stock sleeves would hold 400 hp and I'm sure the 0.5 mm or 0.012" that was removed wouldn't change the strength that much. I would be more concerned about the pistons and a good tune. Specially if your looking to get those kind of numbers out of a 1.6 liter.

Read this:
500HP Stock-Block B16A