No top end power
 

Hey all.
I need help to get to the bottom of something coz it's driving me crazy.
My 95 xj lacks top end power.
I tow a small camper...around 8-900 kg and on the hwy at 100 on a slight incline I'm pretty much flat to the floor. And that just doesn't seem right for a 4.0. Especially since i just rebuilt it.
So. Some history.
Rebuilt the motor. 20 thou over. Bored, New pistons and rings, lifters, timing chain. Head and block planed. Valves reseated etc etc.
Fuel pressure good and holding. New filter. Injectors tested. Pressure reg good.
Newish coil...leads ...cap and distrubutor.
New radiator and not getting hot.
New 02 sensor and 2" exhaust.
New transmission (we dont talk about that!!!)
Diffs regeared to 4.10 for the 31's.

I'm at a loss. :confused:

Any ideas?

Air cleaner?

Rather large pod filter.

Vacuum leak?

I did check vacuum at idle and it checked ok...by the gauge.
As for top end...not sure how I'd check that....suppose I'd have to attach a gauge to the cab.

Does the distributor advance properly under vacuum & mechanical advance?

Heres a 'real time' effect of large pod/sports air filters...they reduce manifold vacuum and will effect the vacuum advance on your dizzy....I had a cruise control unit fitted to an old V8 fitted with K&N Filters....suddenly my cruise control wouldnt 'hold'/would drop out..much head scratching by tge fitter of the cruise control unit, me, many other mechanics....asked a vehicle 'brand' specialist for his input....reply was instant..."have you fitted sports filters to it ?"....yep...."there's your problem...the diaphrams in the carbs are bouncing and your loosing vacuum....fit standard (paper element) filters n see how you go"....no more cruise control issues...better fuel economy , more top end power...reason...vacuum advance was not functioning properly with tge sports filters fitted.....give it a go...no cost in trying....check for air leaks to your vacuum advance unit as well...is tge diaphram operating...easy test...remove hose and 'suck' on hose to dizzy...does engine 'noise' change ???