I tried to search the forums before I posted this but couldn't find what I was looking for.

This is the issue:
My brother has a 2006 Chevy Tahoe 2wd 4.7L

His truck was surging real bad going down the road and it would intermittently stall out also and then at times die. He'd let it sit for a bit and it would start up and get him home but would continue to do this intermittently.

We both at the same time thought it was the fuel pump. So we dropped the tank and put a new one in. It still did the same thing and found that it was indeed getting gas but no spark... So, we changed the crank shaft sensor and it started back up but the surging is continuing and it still dies. Also it's getting starting to get worse.

We are both pretty baffled by it and can't seem to figure it out. Any suggestions?