Got an under carriage dirtier than a... actually some jokes are best left off the internet. But if you wanted to scrub the internet clean Trax HD Degreaser is about as strong as you can get without pouring acid in your engine bay.
It's non-caustic so safe to use on polished intercooler piping and won't leave your inlet manifold looking like it's done a tour of duty but will blast grit and grime from anywhere you can point it at. Available in an easy to use 750ml bottle, or 2.5L and 5L top-ups Trax HD Degreaser is your answer to clean living.