Exhaust "Y" pipe question
 

on exhaust "Y" pipe there are what appears to be 2 small catalytic converts or something looking like 2 of them then when the pipe joints together there is a big or larger looking one. what are the smaller looking ones.

1999 Blazer 4.3 V6

The '98 and up Blazers have 3 catalytic converters. You're exactly right that the two smaller ones on each side of the y-pipe are catalytic converters, or sometimes called pre-cats, and the larger one after the y-pipe is the main cat.

You're correct, they are pre-converters. Some of the replacement "Y" pipes only have 1 pre-converter.

the new "Y" pipe I ordered didn't show the pre-converts in the picture. if the new one don't have them will that cause a problem???

I have a 98 and there is no pre- converter?

I have a 1998 with no pre cats

Pre cats started in 1999, along with the secondary air system.

If your vehicle is 1999 or newer it will.

what is their reason for a pre-cat.

and yes mind is a 1999

the one I order is supposed to be for 99 model, and it arrived today and no pre-cat on it. it from CATCO.

The pre-cats were necessary to meet 50 State emission requirements, (thanks California). The secondary air system keeps the pre-cats from overheating.