just did the upper engine cleaner thing today....did my head in!! proceedure is quite simple enough...though if ur not careful and stick the spray tube in the vac hose in pic one...chances are that it will at some point suck the friggin tube into the manifold as it did with mine....arrgghh. spent half an hr or so takin the throttle body of and pickin out the plastic tube!! best place to spray it is through the BOV vac hose when engine is runnin cause if the tube gets sucked in it wont go all the way in and u can pull it out without takin the engine appart. was expecting the cloud of smoke that was supposed to come out of the exhaust when u rev to purge it but all i got was just a puff of black stuff...hehe. then again i did leave the stuff in the engine longer than the 10min stated cause i had to fish out that damn tube.....otherwise my engine was pretty much clean in the first place. used the remaining can in a 94 prelude that hasnt been serviced in the 3 yrs that my mate has had it for. damn there was smoke everywhere which was a sign that the engine was really dirty inside...so im sure this stuff works!! as for performance, well the car runs smoother than before, that could be due to the motul 8100 that i put it the other day though.
so if ur engine isnt that dirty inside (carbon buildup) then u wont notice much, but its an easy, cheap and simple thing to do and is recomended every 2nd service which i will be doin from now on (and alot more carefully too!!)