i havent really hunted why but i have a really bad shaking chuggle with 215/12v 913inj pumped engine.has a 10 plate.3000gsk red oak injectors,15deg timing,4inch exh and stock charger.it runs really good under power,and like probably all these 3.54 geared trucks,locks up too soon[about 50mph]but the shaking chuggle just sux.i have read that the 913 pumps are a pain to get smooth with a gsk,and i like mine adjusted a fair amount tight and with my 180 pump it didnt ever seem to have this issue period.i have tried two converters,one single and one triple[ran this one a lot w/180 and it was great] and if i can fix this chuggle i will be very happy because this thing really runs hard,boosts to 37 in a hurry,and has great mpg too...please help if you can!!! thanks for reading