rebuilt head but compression lower

first time on forum hope I did this right. recently purchased 1999 tacoma running rough at idle but ok power. Customer had replaced Alternator, battery, and starter. drove a few days rough idle worse, threw code PO301 also found PO300 in memory. visual inspection looked ok changed plugs, looked ok, no effect. Noticed an irregular spit in exhaust, next Compression test cylinder 1=30psi , 2=45psi, 3=170psi, 4=175psi. tore down expecting blown head gasket but #1rear exhaust valve burned bad and pulled up into seat and #2 front exhaust valve obviously burned. Cylinders still showing crosshatch with slight shiny wear marks 1/2 way up on sides, but no galling/scratching. Had head professionally rebuilt. reinstalled using Toyota Head Gasket. redid compression check before running cyl 1=90psi, 2=65psi, 3=105psi ?, 4=110psi ? . lost compression in 3 and 4 what the? decided to chance it and run it. idle now smooth, power improved, but slight rattle when accelerating or climbing (no obvious exhaust leak at idle) rattle only present under load (not rod thump) any suggestions?

 

Assuming you installed the head correctly (especially the torque sequence, usually done in stages)... I suggest you run the engine several thousand miles to allow the new machining to wear in. Then do a compression test and report back.

Rattle under power -- could be an exhaust shield or something else. More details. A video or audio recording would be helpful...

 

Thanks DGXR finally found the rattle. followed my ears but since it only happened under load i put a small tube through firewall grommet and positioned it at varoius places on engine the drove it around found noise most prominent above egr valve upon further inspection found i had missed hooking up the short vac hose between the egr vacuum modulator and the EGR valve who knew that would cause such a noise. as for the compression I think your right it runs good so will retest in several weeks thanks for your input.