2005 Nissan Frontier compression question?

[l[ee]l]

I have a 2005 Nissan Frontier Nismo edition 2wd. It had a recall on the catalytic converters, so I had them cut out. After the converters were cut out it started blowing white smoke out of the exhaust, and has lost compression.

So my question is, what could possibly be wrong with it and what do i need to do to fix it?