Need some help with an engine problem. I completed a B16A SIR2 swap in the fall. Everything was running great until the weekend. I drove it about 30 miles (50km) and it ran fine. Then i washed it and sprayed the engine bay down just with the hose. Then some guy came over and test drove it by himself (I am selling). After he got back I started it and the engine is now studdering (especially in lower RPM). It feels like its misfiring and definately underpowered, but I am not getting any codes. When I accelerate in neutral and hit 4000-5000 RPM it makes a terrible noise (almost like loose heatshields), but over is better. It seems to shake/shudder alot in the lower RPMs when gas is given. Idle sounds OK but is a little more rough then normal but doen't have the shudder. Any ideas? BTW: Plugs, wires, dizzy, timing belt, O2 - are all 3 months old and worked well.