Chevy & GMC Vans

Just purchased my 2000 Astro van with 141k and having numerous problems. On the first day I replaced the fuel pressure regulator on a recommendation from a friend due to rough Idle and P 300 code for random misfires. It ran ok on short trips. Today was the first real drive in it, and it wont accelerate over 40mph once it got hot, and wants to stall at every stop light. SES light on but didn't get a chance to check codes yet (misfires I'm sure). Like I mentioned, I replaced the fuel regulator and cleaned the TB good. I've heard of problems with the spider injection system. Is this something I should be looking at with these symptoms ?
Any suggestions are greatly appreciated...

The solution to this problem was a left bank front O2 sensor...runs great now

Glad to hear you fixed it. Thanks for posting the solution, even if we didn't help you find it. I'm sure it will help somebody else when they read this.

yes, thanks for posting the solution. weird that an O2 would cause a random misfire code and not an O2 code