I ve got n55 135i with jb3 piggy back system. Runs like a champ
never had experience with flash tunes, but people that have done it are happy as well. ( even tho the gains are smaller and $ is way more) .
Intake wise I will be getting an aFe intake for n55 from modbargains.com
It's a bit pricey but after reading all the reviews on it I think it's well worth it. ( btw it's listed for 335, but confirmed to fit 135)
Hope that helps
And yeah... I wish there would be mere action in 1 series forum