Just swapped a b16a (SiR II) into a 95 civic dx.. I've yet to wire the vtec / vtec oil pressure as I wanted to diagnose any strange problems first.. Either way, it throws a code 21 which is no big deal.

Two strange noises I have:

1. At about 2500 rpm there is a strange resonating / rattling noise sort of sounds transmission related but it dissapears before and after 2500 rpm.. Ideas?

2. Inside the car at idle the car literally sounds like a diesel.. it sounds like it has incredibly bad knock, yet outside the car at idle it sounds smooth, even if I use a stethascope it sounds fine, but there is a knocking related to idle inside the car. Ideas?

 

Have you ruled out loose exhaust heat shields? Or exhaust hitting the floorpan?

 

I haven't checked that to be honest but nothing on the exhaust side of things has changed, the manifold bolted up to the old donut O and everything fits like stock, so I don't imagine it could be that.