Recently, i did a build on my lt1. i went forged with je pistons, scat rods, and a gm forged 3.48 crank. I had a cam custom ground for stockish heads by bret buaer. it's a .603/.600 lift cam he designed for my purposes. I have the comp cams beehive springs installed to height (by machine shop). I am using stock lifters which you can run on those beehives without problem. total compression is about 11.45:1 on a 56.6 cc head, .039 gasket and the block being zero decked. I'm using Comp cams pro mag non self aligning 1.6 rockers with gm guideplates and and arp studs. there's my setup, now here's my problem...

The engine clacks pretty good at cold start (not piston slap). the sound is pulsing at the same speed of the valvetrain so it must be there, and i can further prove that. with the valve lash set properly at around 1/4-1/2 past 0 lash, the clacking it quite loud. it gets substantially quieter when the car warms. the only way i have been able to quiet the clacking is to back the valve lash down to 0 lash or even a bit looser. It quiet then, but its now too loose and the rockers are ticking of the top of the valves. I had a 7.150 pushrod in at that time which seemed to make a near perfect wear pattern on the top of the valve. For giggles, i switched back to a 7.20" pushrod and the noise quieted, and it also drove better with less low end studder (the car would stumble quite a bit when taking off from a stop and cruising in 5th or 6th gear). The wear pattern on the 7.20" is worse, but not terrible. I have tried everything possible to get this going. I installed and reinstalled everything correctly. I can't see how the machine shop screwed up degreeing my cam (straight up, no advance or retard) or hoq they could have screwed up installing the springs. Is there any machining required for my stock castings to handle beehives and a .603" lift?? I'm not sure what else to do. the pcm was tuned via tunercat by madz28.com twice and still the same results. The motor runs very well once you get the rpm above 2000. it runs very smooth. recently, i got it running fairly well at 0 lash, but it still has a little clack to it. even when warm, you can sometimes hear the clack speed up when first lightly accelerating from a stop. this tells me there's something wrong in my geometry or something, but I can't tell what. maybe unrelated, but the rpm likes to stay high when you kick in the clutch and start to slow down for a stop sign. I keep backing the throttle body back to close it more, and it's still doing the same. after i floored it through a couple gears, i idled at 3k rpm for a couples minutes and didn't come down lower than 2000 the rest of the way home. this is on all 3 tunes i have for the car. I'm getting no codes thrown at me or anything. I was hoping somebody could help me out. This board was recomended to me from a local board member.
thanks much