Lost power and max speed
 

2005 Town & Country 3.8
Hit 80,000 miles and decided to change spark plugs. I went with the NGK G Power. Gap was low so I separated it to .05 give or take a lil. Also installed new wires. Test drive was very disappointing. On city roads, van has sputtered and stalled and on the highway it can only get up to 65 mph with 4000 rpms and pedal to the floor. Kind of a grinding noise when it gets up there too. I have checked the plugs and they all have signs of firing. The grounds have a white residue and the tip of the plug has carbon. CEL came on but all the Autozone worker said was clogged EGR. He didn't tell me the code. EGR seems fine. My guess would be faulty plugs. Any other ideas before I go buy another batch or just send it to a mechanic??

was this issue there b4 u replaced the plugs?

The wife mainly drives this van and as far as she can tell me is that it sputtered every now and then, but was fine on the highway. We have had issues prior to replacing the spark plugs. CEL light has always been on giving a code for clogged EGR or catalytic converter. The EGR is clean. I've never messed with the catalytic converter. Its too costly for such a minor emissions issue.

maybe the cat has collapsed,and reducing the gas flow,which would stop u from revving it up

also egr may look clean,but could be sticking which could also block the gas flow

I've replaced the EGR valve before. Still pulling p0404 code.

UPDATE: Had the catalytic converter replaced and now the vehicle runs fine. I had the oil changed a couple weeks prior to issue. Should I change it again considering the fact the exhaust is going to be blowing out a lot of debris that has backed up?

that would not mess with the oil so no