86 GMC Sierra Classic 2500 questions

[gmcnoob]

For awhile everything had been going well with this truck thanks to the help I have received here but now I'm back.

It is now pulling oil into the air cleaner housing from the breather. A decent amount of it too. PCV is working fine.

The engine is old and I'm sure there is plenty of blow by but it seems excessive to be pulling oil into the air cleaner. I know a rebuild is probably the answer but are there any other suggestions?

I don't want to keep pulling oil into the air cleaner but I see no other option.

This might be a dumb question but can a different exhaust cause any of this? The old muffler was rusty and full of holes so I just slapped some cheap thrushers on there. Don't know if that could be causing issues.