Some exhaust manifold info.
As most of you already know, the rear manifolds on a Bonneville are different then on Grand Prix etc. I knew that and made sure I got Bonneville manifolds. Well I picked up some ported manifolds off of a '99 Bonneville for my '03. Went to install them and went to bolt up the rear flange, turns out my rear flange and downpipe are larger then the '99'*. My guess is they changed the exhaust around when they chnaged the model in 2000. There'* no way to make it fit. I will use my stock rear manifold ( I'll polish it a little) and use the ported front one. It looks like it will fit ok. Just thought I would let you all know so you won't make the same mistake.
2003 Granite Metallic SSEI 14.5@96
3.5 pulley, Intense PCM, 180 stat, Autolite 104'*, Intense FWI, Borlas, custom Y and chrome Tips, Aeroforce Scan Gauge, MBQuart HU, 12" Power Acoustic Sub, XM Roady XT, Silverstars
(former GTP owner)