Hey guys, recently replaced catalytic converters with stock OEM cats on my 2003 350z enthusiast base with the stock exhaust. 130K miles

Got the car back ran perfectly for 10 minutes then had problems accelerating.

No power in the low end and accelerating hard is very uncomfortable.

Read the codes and p0327 came up about the knock sensor.

Took the car in today to Fontana Nissan. They told me the knock sensor code was not reoccurring and was not an issue.

They then told me I should change every spark plug and ignition coil.

So far they have told me they are just assuming things.

The car at idle will sputter every now.

Say I do need new spark plugs and coils, I was quoted at $1200 for all 6 sparks and coils.

Does any of this make sense? Or are they just trying to get money out of me?

Been reading on the forums of some guys have very similar issues.

Knock sensor code reading, need to change sparks, car doesnt accelerate well, etc.

Any suggestions? If I need to get new spark plugs and coils should I get OEM parts and just pay all that money or get some aftermarket stuff?

Any help is greatly appreciated thanks guys.

EDIT*
During all of this my check engine light never came on once.

 

How many miles are on your Z? Do you know what kind of spark plugs are installed currently?

 

The first thing that came to my mind was a possible vacuum issue such as a leak. I also thought maybe the gasket for the plenum was bad or that someone didn't install the connections back properly.

 

130K, and im not sure what spark plugs are currently in the car. I have only had it for about a year and a half

 

I had the shop check all the seals on the exhaust because I had changed from an aftermarket exhaust to my OEM exhaust and bought all new gaskets. They said there were no leaks there.

 

Did they ground the exhaust near the rear of the car? Not that it would cause your issues, though.

As for vacuum leaks, I was thinking more about the engine compartment.

 

yes ground near the rear.

 

Some spark plug brands can cause drivability issues with the VQ. It's best to stick with what came with the engine (NGK or ND) unless there's been big changes made (race motor, FI, etc). Do you have the ability to simply pull the plugs yourself, and check the brand and model?

 

Unfortunately not the shop has my car right now. However they decided to change out every spark plug I have without asking. So I would assume stock nissan spark plugs?

 

Why assume anything? Ask the tech who was working on it: what spark plug was in there when he started and what did he use to replace it? You should get the used parts back, so you can inspect them and possibly learn something.