I need some ideas how to get something all the way back in the merge of the LS1 hooker y-pipe to open up where the pipe goes into the other one. The hole they cut is only ~1.5-2" tops.

 

I just posted up in this other thread about the Flowmaster merge. U gotta get it, that piece is so worth the $45 that it cost plus labor to weld it in. I tried grinding down my merge in my Pacesetter ORY with a fingerstone and long extension before I installed it. It was a pain in the ***, and did no good. The exhaust sounded raspy and just "ok" unless at WOT. After hearing so many people on this board praise the FM merge, I decided to buy it & have it welded in. Man what a difference! I wish I would have just went with the FM merge from the get-go, but hindsight is 20/20.

 

i did the same, get a FM merge. the sell them in all sizes. if i were you i would get 3in into 3.5in at least, that way it wont bottle neck as much, if you want the least amount of restriction get 3in to 4in with a 4in cut-out reduced back to the cat-back tubing size. if you do decice to go with the later, be aware that you may need some costum work to make the 4in work and fit right. Either way the FM merge gives you a smooth transition and it helps reduces rasp and improves flow.