G'day one and all, hoping to get some info/comments on replacing cats.

LS1/HTV1900 (SS Wags auto) with after market Pacemaker 2.5" stainless system (sureflow cats I believe..)

Have noticed (and had a mate also comment on this without prompting) that I have a 'rattle/noise' coming from the rear of the exhaust (sounds like a stone scraping about - initially I thought the mounting brackets had crap in them) but have since noticed (at low/mid revs') that the power is lacking (if I push the pedal towards WOT then power 'seems' fine). So I have been thinking possibly cats are stuffed (although I could also have a fuel issue given WOT seems fine....). I have also noticed that the tail pipe tips have some strange marks on them that I can not explain:

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Noticed the above when giving my wags a wash the other day (I have just returned from a weeks break down the coast, where the car sat with potentially 'some' salt residue in the tips? - so it could be corrosion?)

Anyway, called the shop yesterday to see if I could get a health check but, place is on skeleton staff for another week, so it was decided that I whip my wags down to an exhaust shop to check the cats (could be collapsed?).

Got her up on a hoist yesterday at Midas and the fella there seems to think that at least one of the cats is stuffed.

Just an F.Y.I, re the fuel, I do have AFR sensors installed and can not see any form of leaning out throughout the rev range (via Aeroforce gauges) - seems a little lean at idle but as soon as any throttle is applied, AFR's 'seem' fine (14's) with the appropriate switch to rich when at WOT (11's) - although, light throttle action does seem to be choked and sluggish.......

Ok, back to the cats question:

I have been recommended Balistics 100 cell racing cats, but fella at Midas seems to think that Magnaflow 200 cell would be better for longevity with very little impact to rwhp.

As always, any comments, suggestions, thoughts would be greatly appreciated. If anyone could also give an indication of cost, I would be most grateful.

Thanks as always,

Carlton