|vertical clamped position with good results. Replace with alan head. When you pull the plenum grind away plenum material so you can get at injectors in future without a plenum pull.
If you replace the injectors, hoses etc recommend a pressure check (45psi) on injectors, fuel rail, etc before the plenum is reinstalled. Easy to do just create a loop with fuel intake hose (after the filter) connected with the fuel return hose with a pressure gage and air supply with shut off valve in the loop. If all OK no pressure drop over time, I let it sit for about 1 hour. Once system pressured up close valve to air supply to prevent air bleed back thru the air compressor to prevent false leak reading. If any pressure leak you need to find it now to prevent problems after assembly. Even new injectors will leak, I had one when I converted to new style.
If you replace fuel lines make sure you use hose for fuel injectors. OEM hose is $$$$ I used GoodYear with excellent results 8 years no problems. In case you wondered the warning noted in link is for outside hose material submersion:
[ http://goodyearrubberproducts.com/2012pdfs/Goodyear_Commercial_Truck_Belts_and_Parts/files/assets/downloads/page0032.pdf ]