Lack of power and lambda sensors

Hello everybody. I have had a long standing performance issue with my 4.6 P38 1996. It basically has a total lack of power, very noticeable on hills. I did have rattly cats when I got the motor, but this seems to have stopped. As I thought they might be blocked, I wanted to do an exhaust back-pressure test, so today I pulled the lambda sensors out so I could see what size fittings I would need to connect a gauge. I gave it a drive with the holes open and it does seem to want to pull better, but still a bit more sluggish than I would expect. I guess its hard to quantify, but should I expect a more significant return of power with the lambdas out if the cats are indeed blocked ?

Picture of my lambda sensors attached - is this typical condition and can they be cleaned effectively - they were switching between rich and lean quite slowly.

The car just passed MOT emissions test, but don't know if that has any bearing on whether cats might be blocked.

Best to stick it on diagnostics and see if the Lambdas are flipping high/low quickly. If they are then they are probably fine.

I had my cheap OBD reader on it and they are flipping over, but probably over 1 second between flips. I think they are meant to flip faster than that, although there is no diagnostic code saying flip time over the maximum. They might needed changed, but I doubt they are the ultimate cause of the serious lack of power that the car has, although maybe a contributory factor ?

I recently had lack of power & turned out to be MAF sensor. See if your reader will display maf sensor reading. If it is low this could be your problem.

My Lambdas are a big sluggish - pick up off idle is sometimes a tad hesitant. But I wouldn't expect them to cause a lack of power. Unless they are not working at all.

About 1 second is correct. There will be a a bit of leeway. As suggested some MAF readings will help bit I think you probably right with the exhaust diagnosis.