i have a 91 f150 with a classic I6 and what i have heard is that if i were to take it to a exhaust shop they would just take everything off up to the manifolds and then run a custom pipe back and then it would split into a y pipe cause my truck isnt dual pipes. they would take both cats off and i was just wondering if any of you have put straight pipes on your inline 6 and does it sound good. and from what i hear its rather in expensive compared to other options.

 

Straight pipes don't sound bad.. by some opinions. Most people will say it sounds like ***, it just aint no v8. A chambered muffler will sound much better.
True duals are possible, just cut off the stock Y pipe with the cats. Only problem is that the pipe from the manifold is like 2 or 2.25 and some shops don't work with pipe that small.
If running true duals on an I6 keep the size small.