h22civic95coupe

Well it all started today, after i installed my new ITR radiator and a new fan ( have no idea if its related or not) but after this instal my car would sometimes bog when you dont give it alot of acceleration, and it happens only below 3-4k rev range, it would keep doing for like 1-3 mins and then go away and go like it always does, when it begins doing it, if you give it alot of throttle it'll just bog a second and then would go normally fast, but when you switch to another gear and dont throttle it, itll just bog again. Anyone have any idea what is causing this problem ? As i said it happend when i installed my radiator(ITR) and a fan(CRX), actually a guy did that for me, and the only problem there was during the instal is that my previous fan blew out the fuse(10A), and we had to put a new one (30A), also right after installing the radiator i let the car run for like 30 mins at his garage, and the engine light came up, which happend again after like 2 hours of driving, Oh, and he also had to unscrew the exhaust manifold, right where it connects to the downpipe, just so you know the whole story..