Npi heads just need a little love along with the pi cams. Pi heads out the box perform excellent, but on an otherwise stock 5.4l, their is no diffrence in power level between the two, same compression ratio. Cammed, long tubed, free flow intake,...no difference. The piston deck needs to be zero before any real performance starts to happen and this is done by decking the block .100" or buying 5.4l specific pistons $800!
You see, a stock 5.4l piston resides .100" down in the bore. This is perfect for an engine in a truck, pulling 10,000lbs, but not what we hungry power Americans want. Keeping that tight "squish" is were performance is at.
The exhaust is a pain, long tubes are the toughest. Although longtubes promise 20rwhp regardless of boltons, they are not an easy fit. Some have done it with success, but at the expense of room. Raising the engine for clearance, eliminating hydrobooster/brakes/powersteering. The stupid steering shafts location causes the most problems. Its dead center where the tubes need to be. Although im basing this on older type long tube designs, newer designs may be available. Some longtubes have the front tube routing over top the flange to reduce the cluster of pipes crowding the steering shaft. Also the frame rail on the passenger side is really close and iirc long tubes clear quite well. Its the stock manifolds that rub a little, but grinding the area eliminates the rub.
