I put bg244 in mine to clean out the carbon in the engine & use it every 7,500 miles. Supposed to be very good by all accounts. I got mine from power enhancer but even with their coupon code it was still cheaper on Ebay.
Sorting out my crankcase filter & red charge pipe, may have a delve into the swirl flaps or at least have a look for them & clean out the egr & intake manifold.
I bought a wire wool brush attachment for my drill re the exhaust... son cleans em but there are dirty again 150 mile later though.