Is this a decent combo? Any ideas how to make it run better
A while back I bought a 99 z28 vert LS1 6spd car in amazing condition. Incredibly clean, 100% rust free with a perfect body and paint aside from slight spidering of paint on the front bumper cover due to someone bumping it in a parking lot at some point (it also came with a new unpainted SS hood so I figured I'd get them both painted at the same time. The seats had been recovered in black leather with gray inlays with Z28 embroidered into the headrests and the rest of the interior was immaculate..
So anyway now on to my actual question. The car had 65k on it and shortly before I bought it the previous owner had done some mods. The short block was left stock but he swapped the stock cam for a BTR Stage IV Cam (Gross Valve Lift .620 int .593 exh Duration @.050 int 235 exh 242 on a 111 lsa), he went with a new chev perf hd timing chain, chev perf HV oil pump, chev perf ls7 lifters, ls chromoly pushrods 7.4 long, new timing cover gasket, chev perf LS1 multi layer head gaskets, and replaced the stock heads with some 799 castings that were supposedly lightly ported and had the valves replaced along with the new springs from comp cams which came with the cam. He topped it off with a FAST 92 intake and FAST 92 TB and resized 36 lb injectors, factory MAF sensor and a racetronics fuel pump (Wire harness still in package, I'll install it at some point). EGR, AIR, and cruise control were all eliminated. It also has pacesetter ceramic long tubes, y-pipe, and slp loudmouth II catback, but does have dual flowmaster cats and downstream 02 sims in order to pass emissions/inspection in my state (New Jersey, all they check is that it has cats installed, o2 sensor readings, and a lack of trouble codes, no actual sniffer test.
My main questions are as follows: Is this a decent combo? To me it seems like it would do better on a larger cube engine, but I don't know much about ls builds. I'm not sure how/where it was tuned but he did till me that one shop he took it to said that it was costing him at least 30 rwhp and had other issues. Since I've had it I've noticed it runs best in hot weather, good idle, good power, no issues. The colder it gets the worse the idle gets, sometimes stalling, I have to allow it to warm up to operating temperature before driving it or it will stall quite often, even after warm it seems to hunt for an idle and sometimes stall. The strange part is if I shut it off and allow it to sit for 5-10 mins after it's warm it will run perfectly. Also it occasionally throws an alternator DTC, I forget the actal code but I think it's terminal L or something along those lines, it will occasionally throw a knock sensor code and a TPS code, I tried replacing the throttle position sensor with no change as well as checked the wires for continuity and resistance and found no problems, I've checked the reading from the tps from closed to wide open and all appears normal. Also while looking at freeze frames for the code there is always a normal reading showing. I was told by the previous owner that he was told these codes are related to the tune.. Not really sure where to go from here, any advice would be appreciated, maybe it's time to buy some tuning software and try to learn?