I ran stock 340k mile up-pipes on my LLY when I had a Danville 68mm Stage 2R 4094 installed with 60% overs and a 10mm. I do not think you need up-pipes unless you've distorted the stock ones or they are leaking. IMO there isn't a huge performance gain on them until you really start pushing the envelope.
That said, it doesn't hurt to put in a quality replacement if yours are high mileage, showing cracks, or leaking. I don't think you'll benefit from getting larger manifolds.
alright so im getting down to the final wire just got a few more things to sort out before I install the turbo. im on the fence of what downpipe to go with I like the look of the ppe stainless 3in down pipe but don't like that I can see a weld near the v band flange on the turbo connection which to me is turbulence or flow restriction I may be over thinking this. what other companies out there make stainless 3 in lbz down pipes that are mandrel bent and smooth yet still retain the lower mount tab for the passenger side up-pipe flange .plus if I go with ppe cause no other stainless ones are mentioned how is the fitment of it ive heard horror stories and I will be removing the heat sleeve and dei titanium wrapping it cause it looks better than the sleeve to me. any and all options are welcome thanks:thumb: